A simple example of EIGRP route manipulation using change in metric OR applying offset list.

In this example we have taken a setup which is more or less a simulation from cisco example but I have done a little modification to it.

We have 4 routers and 1 ether router/switch. The router R1 is connected to R2 && R2 connects to R3 and R4 over different subnets. R3 f0/0 shares 4.4.4.1 /24 subnet with R4 f0/1, 4.4.4.2 and interface SVI vlan 3 with IP 4.4.4.3 /24.

The connection style is given below:

R1(f0/0    {.1})<->R2(f0/0   {.2})= 1.1.1.0/24

R2(f0/1    {.1})<->R3(f0/1  {.2})=2.2.2.0 /24

R2(f1/0    {.1})<->R4(f0/0  {.2})=3.3.3.0 /24

R3(f0/0    {.1})<->R5(f1/1  {.3}{SVI})=4.4.4.0 /24

R4(f0/1    {.2})<->R5(f1/2  {.3}{SVI})=4.4.4.0 /24

Objective:

To learn the 4.4.4.3 sub-network IP  from R5 and making the R2-R3-R5 as preferred route and R2-R4-R5 as backup one. 

R1 set up:

interface FastEthernet0/0

 ip address 1.1.1.1 255.255.255.252

 duplex auto

 speed auto

!

interface FastEthernet0/1

 ip address 192.168.1.254 255.255.255.0

 duplex auto

 speed auto

router eigrp 100

 network 1.1.1.0 0.0.0.3

 network 192.168.1.0

 auto-summary

R2 Set up:

interface FastEthernet0/0

 ip address 1.1.1.2 255.255.255.252

 duplex auto

 speed auto

!

interface FastEthernet0/1

 ip address 2.2.2.1 255.255.255.252

 duplex auto

 speed auto

interface Vlan2

 ip address 3.3.3.1 255.255.255.252

!

 router eigrp 100

 network 1.1.1.0 0.0.0.3

 network 2.2.2.0 0.0.0.3

 network 3.3.3.0 0.0.0.3

 auto-summary

Above in R2 I had only one routed port and other one was switch port so I chose to do something usually different and made one SVI 2 0f 3.3.3.1 putting the vlan 2 on f1/0 of R2 which then will connect router R4 port f0/0 IP 3.3.3.2 as above.

R3  Set up:

interface FastEthernet0/0

 ip address 4.4.4.1 255.255.255.0

 duplex auto

 speed auto

!

interface FastEthernet0/1

 ip address 2.2.2.2 255.255.255.252

 duplex auto

 speed auto

router eigrp 100

 network 2.2.2.0 0.0.0.3

 network 4.4.4.0 0.0.0.255

 no auto-summary

R4 Set up:

interface FastEthernet0/0

 ip address 3.3.3.2 255.255.255.252

 duplex auto

 speed auto

!

interface FastEthernet0/1

 ip address 4.4.4.2 255.255.255.0

 delay 18                                                     //This delay was used to manipulate the path by delay. change.

 duplex auto

 speed auto

router eigrp 100

 offset-list 99 out 300 FastEthernet0/0

 network 3.3.3.0 0.0.0.255

 network 4.4.4.0 0.0.0.255

 no auto-summary

!

ip http server

ip classless

!

!

access-list 99 permit 4.4.4.0 0.0.0.255

R5 Set up:

interface FastEthernet1/1

 switchport access vlan 3

 no ip address

 speed 100

!

interface FastEthernet1/2

 switchport access vlan 3

 no ip address

!

interface Vlan3

 ip address 4.4.4.3 255.255.255.0

!

router eigrp 100

 network 4.4.4.0 0.0.0.255

 auto-summary

Identified solution to make R2-R3-R5 as preferred route:

1.  Check the FD/AD of the route to network 4.4.4.0 with sh ip eigrp topology command

R2#sh ip eigrp topology

IP-EIGRP Topology Table for AS(100)/ID(3.3.3.1)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

       r - reply Status, s - sia Status

P 1.0.0.0/8, 1 successors, FD is 28160

        via Summary (28160/0), Null0

P 1.1.1.0/30, 1 successors, FD is 28160

        via Connected, FastEthernet0/0

P 2.0.0.0/8, 1 successors, FD is 28160

        via Summary (28160/0), Null0

P 2.2.2.0/30, 1 successors, FD is 28160

        via Connected, FastEthernet0/1

P 3.0.0.0/8, 1 successors, FD is 2816

        via Summary (2816/0), Null0

P 3.3.3.0/30, 1 successors, FD is 2816

        via Connected, Vlan2

P 4.0.0.0/8, 1 successors, FD is 30464

        via 3.3.3.2 (30464/30208), Vlan2   //**This goes in routing table to reach net of 4.4.4.0 /24- from R4

        via 2.2.2.2 (30720/28160), FastEthernet0/1

P 192.168.1.0/24, 1 successors, FD is 30720

        via 1.1.1.1 (30720/28160), FastEthernet0/0

One way is to change one of the metric used in route selection of 5; Bandwidth, load, delay, reliability and MTU.

For ex. if we change the delay of interface f0/1 of R4 the metric will become poor the traffic over R3 will be preferred.  Go on to the interface and change the metric to any(in tens of microsec) like delay 20.

This will spoil R4 to be the best route to reach network 4.4.4.0 and R3 thus will be preferred.

Note: One often should consider while changing Bandwidth as it will have a huge impact on route calculation and might ruin all possibility of either becoming backup route OR no route at all.

Second way, is through manipulation of sum up of all metrics using offset list.

If we go back to set up of R4 you will observed there I've used access-list:

access-list 99 permit 4.4.4.0 0.0.0.255

This states that a standard ACL will permit all route with source 4.4.4.0.

Now this ACL is to be called in eigrp subcommand of R4,

router eigrp 100

 offset-list 99 out 300 FastEthernet0/0

The above states that ACL 99 passes out with a modified composite metric  and added with value 300. So earlier the FD/AD of R2 was

4.0.0.0/8, 1 successors, FD is 30464

        via 3.3.3.2 (30464/30208), Vlan2

        via 2.2.2.2 (30720/28160), FastEthernet0/1

Now it is,

4.0.0.0/8, 1 successors, FD is 30464

        via 3.3.3.2 (30464/30208), Vlan2

        via 2.2.2.2 (30720/28160), FastEthernet0/1

oops!!!!!  It didn't change. 

Wow, I just happened to have found out the reason. The ACL above has 4.4.4.0 as source but my R4 is summarizing the whole route to class A boundary because we all know EIGRP's romance with summarization. So all you need is to add the command no auto summary and the problem is solved or the other way change the ACL with 4.0.0.0  255.0.0.0 cmd. Either way you achieve the same result.

Output now on R2 after disabling auto-summarization is below:

P 4.4.4.0/24, 1 successors, FD is 30564

        via 2.2.2.2 (30720/28160), FastEthernet0/1        //**best path via R3

        via 3.3.3.2 (30764/30508), Vlan2                       //** path via R4 as backup now

Now path via R3 become the best path.

This way you can have some fun with change in metric or applying offset list to tell that I will spoil this route. Remember MTU as metric is a container and not used in route calc for best path.

Share, If you have something new or to disagree.

Cheers!!

LW Access Point registry with WLC

The WLC management interface is used for L2 communication between WLC and APs.

A WLC has one or more AP manager interface for L3 communication between WLC and LAP after AP discovers the controller.

Sequential events for LAP to register with WLC:
1. The LAP issues a DHCP discovery reequest to get an IP address unless it has previously had a static IP address.
2. The LAP sends LWAPP(Light Weight Access Point Protocol) dicovery request to WLC.
3. Any WLC the receives LWAPP discovery request responds with an LWAPP discovery response message.
4. From multiple discovery responses LAP chooses the WLC to join(The WLC with least connection is preferred).
5. The LAP then sends an LWAPP join reuqest to the WLC & expects a LWAPP join response.
6. The WLC validates the LAP & then sends an LWAPP join response to the LAP.
7. The LAP validates the WLC which completes the discovery & join process. The LWAPP join process includes mutual authentication and encryption key derived.
8. The LAP registers with the controller.

Hope I could make it easier as it is. :)

LACP SIM

First we have to configure the vlans on the switches.
To make a switch  root use the following command and understand what it does to switch A or switch B spanning tree database:
Spanning-tree vlan 11 root primary
By using above command on the switch,  it will try to become the root for vlan 11 by reducing its bridge priority by 8192 default. Try it for as many vlans as you need on the switch you want.

First check the vtp config on both the switches and if either is server than create vlan on server and it will be propagated to client provided domain name and md5 matches. If both are in transparent mode please add vlan to their respective databases by getting into global command
config# vlan 21 name engineering      etc....

create/Verify if vlan 21,22,23 exist on switch A/B, if yes then good or else create it.
Assign ports properly to their respective vlans.
All the ports that should transition to forwarding must be port fast enabled. This saves the switch-port transition which normally takes 30 sec of blocking to listening to learning and then forwarding. Use the interface range command for quick configuration or use individual but you need to be quick.

Make the vtp mode of B same as that of switch A.
For Switch B to be in same spanning-tree mode as switch A, run a show spanning-tree command or show run on Switch A will also show the configured spanning-tree .

Configure svi vlan 1 on switch B if it doesn't exist and assign it the required IP  and use no shut.

Interswitch connectivity:
1. For trunking use dot1q as it requires tagging unlike isl which encapsulates and is cisco prop.
2. Allow vlan on the trunk link only by using switchport trunk allowed vlan vlan_number. This needs to be run on port which has to be configured for trunking purpose be it one port or bundles of port.
3. For maximum use of available bandwidth one can combine many port under one port-channel so that the spanning tree is not required as loop won't happen and collective capacity of the link also is increased many times.
For the above to work do following:
1. Configure individual port which then is to be trunked but on port-channel only.
2. use show run to check if it has any configuration done on it that is not in line with config of other port it has to be bundled with. Make sure it is not in any access-mode otherwise it will make a port channel for that vlan only and not multi-vlan. Normally we don't make configuration on member but we do it on the etherchannel which is then applicable to members as whole. This is always the good way.
3. Use non proprietary protocol LACP. It can bundle up-to 16 ports as such.
Use following cmd on member interface;
channel-protocol lacp
channel-group xyz(number) mode (active/passive)
Then create a port-channel interface with xyz(number) on config mode and do trunking configuration on it. Make sure you assign right native vlan to the port channel interface.
Do the same config on the other side of the switch. It is up to you to decide which switch will initiate lacp bundling by choosing right mode.

Good luck!

VTP LAB SIM 1

For lab of vtp lab sim-1 the interface connecting both switches ALS and DLS must be in trunking mode to support vtp and updates. So first of all you should configure them in trunk. 

Secondly, place all config of vlan creation/add/deletion etc. on DLS switch as it is in distribution layer and is in server mode by default as per any campus style architecture. The DLS is server and ALS is client. ALS will take all vlan config via VTP updates from DLS. The vtp messgage type includes:

-Summary advertisements
-Subset advertisement
-Advertisement requests
-VTP join messages

Use the same domain name for it to run with MD5 match if provided.  Always don't forget to check the md5 hex value which should be same.

Run ip routing command for DLS switch to make it understand that the switch will be used as multi layer switch. So that it will route packets from one vlan to other.  Subsequently, create vlan SVI with proper vlan id and give them their IP address. At least one port must belong to that vlan SVI to come up otherwise the protocol will always show down while L1 connectivity remains up.

loop guard, root guard, bdpu filter, bpdu guard and UDLD

The loopguard- It is used to detect the loss of bpdu from a designated port to an alternate or root port. So suppose there are three switches a, b, c and A is root bridge connecting B through Fibre media and one receiving link for B goes down. The BPDU sent by A is heard by B but no otherwise. Hence, there is a situation of loop gone undetected by the Topology.
Hence loop-guard in this case will prevent the loop by putting the port in loop-inconsistent state. This is self remedial after some span of time once the bpdus are heard back again.
The loop guard is per-port and per-vlan basis. So when there is a case of trunk only for that specific vlan will the port go in loop inconsistent and no the whole trunk port.
Loop guard on ether-channel considers whole port-channel & will put the channel is loop-inconsistent should the bpdu are not received.

***************************************************************

Root Guard- It is used to put the port in root-inconsistent state when a bpdu of superior nature is heard via that port. This puts the port in listening phase which is then shifted to forwarding phase. Root Guard will not allow the port to become root port or in short it will not listen any good bpdu from this port which posses the capability to become root bridge.

***************************************************************

Bpdu filter- Suppose, port fast is enabled globally with cmd spanning-tree portfast default, then all the access ports are given the status of port fast dynamically. Now, if a bpdu is received on any of the port fast enabled port the port loses the port fast featured state and starts acting like a normal port which then takes 50 sec if reset to forward traffic.
In such case we may want to enable  bpdu filter globally for all port fast ports. This will then stop the transmission of bdpus across the ports irrespective of passage of traffic. Isn't it a wonderful idea?
But imagine if someone connects one more link to that switch,say switch A and B already had a link and now there is one more link and switch A had port fast+ bpdu filter so switch A and B are now in tactical loop but because of bpdu filter they can't exchange the bpdu hence no detection of loop is possible. So, in this case bpdu filter is a mayhem. BPDU Filter is per port basis.

Remember, if the port with bpdu filter enabled receives any bpdu it loses the portfase status and bpdu filtering cease to work. In such case the port starts entertaining STP.

*************************************************************

Bpdu guard- It is used to put the port in err-disable state should the port receive any bpdu. Given the belief that the configured port is a port fast and only a host must connect it and not a bridge this port should have bpdu guard enabled on it. Once in err-dsabled you may either reset it manually or use err-disbable timeout feature.

*************************************************************

UDLD: It is a failure of bdpu transmission caused by failure of copper/fibre medium. So suppose Switch A, B, C are connected to each other in a circle via fibre media where one link of it is used to transmit and other to receive. If transmitting link fails and receiving still works the loop will take place. To prevent such possibility the administrator can use UDLD feature. This feature when enabled on port, used a udld signaling mechanism where udld peer send each other at 01:00:0C:CC:CC:CC and expect a reply over the receiving link. If this is not heard the port is put into err-dsable state

You may refer for more explanation:
http://blog.ine.com/2008/07/05/udld-modes-of-operation/

simple spanning tree 802.1d, we have three ether switch on gns3

In this article of simple spanning tree 802.1d, we have three ether switch on gns3.

Switch AAA has vlan bia(built-in-address)  c400.0b14.0000 , switch BBB has vlan 1 bia c402.0b14.0000 and switch CCC has vlan bia c403.0b14.0000. Hence, assuming the AAA and BBB came up first, they sent their BPDU to each other with fields like Protocol ID,  Protocol version, BPDU type, flag, TCN, Root Bridge ID, Sender's bridge ID, Root Path cost, Port ID, Hello time, Max age, Message age, Forward delay.

Some overview about STP:

1. Switches send BPDU at every 2 sec interval by default.

2. Message age and max age is 20 sec by default.

3. Forward delay is 15 sec which is used in interval.

4. Any port takes maximum time of 50 seconds to reach the forwarding state from blocking. This can be broken into (Blocking to listening->20 sec, listening to learning MAC-> 15 sec, learning to Forwarding packets-> 15 sec)

5. BPDU types are: Configuration bpdu, TCN BPDU, TCN acknowledgement bpdu. A BPDU has 13 fields and it is important to know them each, that will help in understanding RSTP and other protocols further.

6. Switch A if is root and switch B connected to it over 100mb bandwidth than its designated cost is 0 to reach root A and if one more switch C is connected to B over 100 MB again then its DC cost will 19 as the cost is pre-specified for all link capacity.

** Designated cost is compared when the cost capacity of link is equal. If both links are 100mbps then DC can be taken into account. If bandwidth is different or altered like one is 10 and other is 100 Mbps then DC might not show the expected result even if it is 0 and the port will not become root port.

Continuing with our two switches AAA and BBB, both will claim each other as root bridge and will have their own sender id in bpdu.

AAA: I am the root bridge with my bpdu packet as below. Similarly,

BBB: I am the root bridge with my bpdu as just having my own MAC address(right).

Both switch now will compare each others and switch BBB found that it's MAC is of higher ID as sum of bridge priority+ mac ( mac being higher of BBB). So, now switch BBB will use all bpdu and will put mac add of AAA as it is lower in Root bridge ID field. On Ethernet switches lower is always the better. So here Root bridge is AAA.

Now CCC also has come up in similar fashion connected to AAA F1/1 and BBB F1/3.

CCC: Hello, I am CCC with mac c403.0b14.0000 and I am the root bridge in my BPDU(sent to AAA and BBB).

AAA sends it BPDU with self as root bridge & sender bridge ID and BBB also sends its BDPU with root ID that of AAA and self sender ID. Switch CCC compares its bridge ID with AAA and CCC, founds itself in poor to both. Similarly, BBB and AAA also compares and found CCC's bridge ID is higher and poor so no need for new root bridge election. Thus from now onward CCC and BBB will send all BPDUs with Root bridge ID that of AAA and self sender's ID. Ex:

BBB bpdu

**Root Bridge facilitates in mitigation of any bridging loop but remember root bridge AAA  itself doesn't thwarts the loop. 

Loop is broken when any non root bridge finds itself in a position where it received BPDUs with same root bridge ID from two of its ports and then it compares this with the initial results of comparison with its neighbors mac addresses, of course after comparing the cost to reach the root. It also means in technical jargon that a switch has two root ports which is a reason for loop. A switch can have as many ports to reach all friendly non root switches and we call those ports as designated forwarding ports but a switch must not have more than 1 port to reach the root. This is how a switch calculates Spanning-tree.

AAA spanning tree status;

BBB spanning tree status;

CCC spanning tree status below; please see the F1/3  here is in blocking state for #3 reasons, first the CCC lost the root bridge by all means because of higher mac + bridge priority(32768), secondly the cost to reach AAA root is less via f1/1 which is 0 (designated cost) than via f1/3 which is 19, thirdly F1/3 is greater than F1/1 and as I said lower is always better in three switches. 

The situation would look something like below:

CCC interface f1/3 is in BLK state

 

Now, we will extend couple of ether switches to CCC and BBB and will try to understand what their behavior will be one by one on the tongue tip.

Shown to the right, I have connected a DDD name switch by interface f1/4 to CCC. It is obvious DDD is now like a leaf and doesn't have anything next to it. So since AAA is the root, DDD will have f1/4 as the only way to reach the root. The problem occurs when switch DDD sends a BPDU with better and lower bridge ID. This will cause to CCC then to BBB and AAA to consider DDD root if it succeeds.

**Root bridge is a hallmark entity in any L2 architecture through which all other switches try to identify themselves in the positional arrangement under VLAN.

Similarly, if Switch EEE is connected to BBB as DDD is to CCC then it will show similar effect with EEE also acting as leaf bridge.

The output for EEE is,

EEE#sh spanning-tree brief

VLAN1

  Spanning tree enabled protocol ieee

  Root ID    Priority    32768

             Address     c400.0b14.0000

             Cost        38

             Port        45 (FastEthernet1/4)

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32768

             Address     c40a.07e8.0000

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time 300

Interface                                                                   Designated

Name                           Port ID Prio    Cost  Sts        Cost      Bridge ID                         Port ID

-------------------- ------- ---- ----- --- ----- -------------------- -------

FastEthernet1/4           128.45   128    19      FWD    19        32768 c402.0b14.0000     128.45

Now, I will connect DDD and EEE on a common FE link f1/5 and a loop is bound to occur between AAA, BBB, EEE, DDD, CCC in a circle:

A tongue tip calculation involves calculation spanning tree the time you understood their bridge ID and the pattern of already blocked ports. Since f1/3 of CCC was already blocked so a topology was loop free until f1/5 on DDD and EEE was brought in. The moment I introduced f1/5  on DDD 7 EEE all switches could hear root bpdu on two of their ports. If to believe that AAA, BBB and CCC already had their understanding of what to be blocked, it was now turn of newly connected EEE and DDD over F1/5  to exchange BPDU and negotiate what to be blocked.

DDD and EEE didn't block f1/4 ports because it has least cost to reach the root AAA with 19(DC). If 1/4 is blocked, the cost could escalate to 19x2=38. That's DDD would reach AAA via EEE and then via BBB. Same is applicable for EEE should 1/4 was to be blocked. Thus we can conclude that given the least cost parameters one can reach the root AAA, the bridges can choose the best path depending on links bandwidth  and port priority solely than by administrative changes(least recommended).

Below is the EEE spanning tree output:

EEE#sh spanning-tree brief

VLAN1

  Spanning tree enabled protocol ieee

  Root ID    Priority    32768

             Address     c400.0b14.0000

             Cost        38

             Port        45 (FastEthernet1/4)

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32768

             Address     c40a.07e8.0000                                                        ** EEE vlan 1 MAC address

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time 300

Interface                                                           Designated

Name                         Port ID Prio Cost  Sts    Cost       Bridge ID                         Port ID

-------------------- ------- ---- ----- --- ----- -------------------- -------

FastEthernet1/4        128.45   128    19  FWD  19         32768 c402.0b14.0000   128.45

FastEthernet1/5        128.46   128    19  BLK    38        32768 c409.0b14.0000   128.46

Now, let's make one more test just to check where we have reached with  our understanding.

We will connected a FE between BBB and DDD with bandwidth 100mbps.

The answer will be simple to at present prevalent topology. A new loop will be introduced with f1/6 between BBB & DDD.

So to thwart that again, who will block depends upon whose BID is what? DDD has poor bridge ID to CCC and BBB thought cost equates to 19(DC) for both. But since BBB has lower BID to CCC so DDD's f1/4 will go down to blocking. But if I reduce the cost of f1/6 link of DDD to 10 mbps, then certainly F1/4 will come and up and take the role of root port to reach the root bridge.

RIP version1 : #1

In this example I share with you the logic and simple tricks with RIP version1. 

Look at the picture provided:

In this picture we have taken two Cisco routers named R1 and R2. Both connected by LAN serial link, clock 64k, network 20.20.20.0 /24. Router R1 connects to two ethernet LAN segments with subnets 10.10.10.0 /24 and 10.50.50.0 /24. Router R2 connects ethernet LAN segment at 10.20.20.0 /24.

When router one is up it has its routing table with 10.x.x.0 and 20.x.x.0 in its  routing table showing directly connected. But since R1 knows it has two 10.x range subnets hence it has wrapped it under classfull boundary of class A. Any routing table gives highest priority to what it has on its interfaces.

Similarly, R2 knows 20.x serial range with 20.20.20.2 IP, s0/0 has not wrapped 20.x range to classful boundary since it has only one of its kind as on R1.

If suppose we were to have one more 20.x range like 20.30.30.0 it would have been wrapped to 20.0.0.0 /8 and then represented variably subnetted.

Well lets get to the point. Running RIP Version 1 which hardly forms neighbor and broadcast  to every member interface by default. Even if we have not set RIP v1 on R2 , R1 will send update to all its connecting interfaces like f0/0, f0/1 and s0/0. point to be considered here is no one wants update to be sent on fast ethernet segments as we don't have rip neighbors there.

There is one more thing to be noted when we put network subcommand under router rip that we indirectly tell the RIP to send updates on those networks than to advertise the networks. So suppose if you have written

Router rip

ver1

net 10.10.10.0

net 10.20.20.0

net 20.20.20.0

The rip will summarizes them to class full boundaries of class A and advertise networks like 10.0.0.0 to interfaces members of RIP other than owner interfaces.

Now the logical mystery is that R2 though will receive the update via 20.20.20.1 s0/0 for 10.0.0.0 but it will not put in its routing table unless the 10.0.0.0 /24 entry for f0/0 is put down or disallowed.

When we put f0/0 down on the R2, it will learn 10.0.0.0 update from R1 and immediately will put it in routing table of R2 like this

When f0/0 on R2 was put down:

Gateway of last resort is not set

     20.0.0.0/24 is subnetted, 1 subnets

C       20.20.20.0 is directly connected, Serial0/0

R    10.0.0.0/8 [120/1] via 20.20.20.1, 00:01:59, Serial0/0

Now if we put F0/0 of R2 up the entry will be something like this

Gateway of last resort is not set

     20.0.0.0/24 is subnetted, 1 subnets

C       20.20.20.0 is directly connected, Serial0/0

     10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C       10.20.20.0/24 is directly connected, Serial0/1

R       10.0.0.0/8 [120/1] via 20.20.20.1, 00:00:29, Serial0/0

Router(config-if)#

Now if there is a request for 10.x.x.x network it will be matched with highest bits and priority route will be directly connected f0/0 otherwise the 10.x.x.x via RIP on R1 will become the chosen route.

Basic overview of 802.1x authentication

This topic discusses in brief how .1x works in port based authentication.

Duplicate IP address

Since not from very long, we've been coming up with issues of Duplicate IP address source by some MAC or issues where a ping to an IP gives two replies or the origin gets two replies say it other way.
I am actively working on it and sooner or later definitely i would come up with some idea on it for
1. Why it happens and what causes it?
2. What causes it and approach we need to handle it?
3. Best way to sort this out?

to be continued..

What made me write this blog ?

Well, I have an inquisitive mind and in this century I am no shy to tell you that a lot more than 100s of things keep bumping my head and I nakedly accept lack of perseverance have made all gone into dust box. But wait, wait! Lets not do that here again. Lets make an advance, I would say others have been following the example Of;  and you don't need to lead at all as of now. Guru told me that networking can't be done alone. Yes, as in its name has, networking is not done alone.

We'll during the period try to explore from surface to depth of all range of concepts from basic understanding of bits to diving into huge in-depth of routing and its finest elaboration but simple way.
I would try my best to give you a view of my research with best possible explanation so that you may try that at your home with GNS3 if those $10-$1000 aren't worth spending buying network devices of switch & router range especially costly Cisco ones. Okay, lets not talk commercial here: enough conjecture.

During my time here on my blog I'll share everything with wow understanding of vlan in damn simple style to all concepts on switching, data formation, to frame traveling, the broadcast in depth to unknown unicast, data plane to control plane logic, spanning tree and it's type like PVST(+), RSTP, MST etc, gateway load-balancing and its types, dot1x, L3 switching and MLS and how it differs(CEF, process switching, fast switching), AAA concept, Ether-channel and lots more(routing in later session).

Now you would want to ask : Hey! have learned all this from CCNA/NP nuggets ?
Well, of course you would have but that's where the challenge lies. Nuggets prepare us from exam point of view with limited but clear knowledge sharing, however, we here will try to build things which will give us a sense of not being an ordinary professional IT in a corp or just a CCNA/NP but  make us stakeholder in the business of what we do and how we do it differently than others. I'll share with you self executed experience, by which if not awestruck, you will also find a sense of achievement when you would have executed it at last. Something good to share with your buddies and a sense of pride, making you stand in league of explorer and believe it, this will be the other way as well where you may end up putting your own ideas and exploration on the planet of networking jungle. Put up and I urge you to put some of the toughest challenge and questions around and then we'll shoot that together.

All the best on my behalf and hope you'll enjoy the journey!

Abstract

Whatever the subject is, an abstract of an idea a vague understanding of concept is must. You do not need to be an expert nor should be a book worm, but when get a chance to design the solution to a problem be clear with what you've to implement with exclusive synchronized plans, ideas & skills.