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Weekly Open Ended Question #7
Mar 9th
The answer to the sixth question has been added to the post.
Seventh question:
What is ODR? How does it work?
Please post answers in the comments (without Googling)!
Troubleshooting Lab #2
Mar 6th
I don’t usually post on weekends, but I want to try out an idea for troubleshooting labs (and I’m bored). This is the second in the series. We got a lot of answers for the last one, most all of which were correct. I’ve started requiring approval for all comments, this way the answer won’t be posted immediately after I make the post. I think this will be more fun and encourage more people to answer.
This time we’ll have the topology and a .net file, but I won’t be posting configs and you guys won’t be able to do “sh run”. I’ve saved the configs inside the .net file. Run the topology and login with username “tshoot” and password “tshoot”. This user only has privilege level 1, so show commands will be available, but show run will not be. Obviously you could get around this pretty easily, but that would defeat the purpose. 
Troubleshooting Lab #1
Mar 5th
This will be the first in a series of troubleshooting labs. I will post a topology and the issue I’m seeing. Hopefully you guys will attempt to solve it and post your ideas, questions and solutions in the comments.
We’ll start with a relatively easy one. Today we are having an issue with BGP neighbor relationships not forming.
Here’s our Topology:
Here’s R1’s config:
hostname R1 ! ip cef ! interface Loopback0 ip address 1.1.1.1 255.255.255.255 ! interface Serial0/0 description To R2 ip address 10.1.1.2 255.255.255.254 ! router bgp 5000 no synchronization bgp log-neighbor-changes neighbor 2.2.2.2 remote-as 6000 neighbor 2.2.2.2 ebgp-multihop 2 neighbor 2.2.2.2 update-source Loopback0 no auto-summary ! ip route 0.0.0.0 0.0.0.0 10.1.1.3 |
And R2:
hostname R2 ! ip cef ! interface Loopback0 ip address 2.2.2.2 255.255.255.255 ! interface Serial0/0 description To R1 ip address 10.1.1.3 255.255.255.254 ! router bgp 6000 no synchronization bgp log-neighbor-changes neighbor 1.1.1.1 remote-as 5000 neighbor 1.1.1.1 ebgp-multihop 2 neighbor 1.1.1.1 update-source Loopback0 no auto-summary ! ip route 0.0.0.0 0.0.0.0 10.1.1.2 |
Now some show commands:
R2#sh ip bgp summ BGP router identifier 2.2.2.2, local AS number 6000 BGP table version is 1, main routing table version 1 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 1.1.1.1 4 5000 0 0 0 0 0 never Active R1#sh ip bgp summ BGP router identifier 1.1.1.1, local AS number 5000 BGP table version is 1, main routing table version 1 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 2.2.2.2 4 6000 0 0 0 0 0 never Active |
We see that the relationship will not form. You guys tell me why.
I’m attaching the .net file, with it and the configs above you should be able to replicate this easily.
The Troubleshooting Lab #1 .net file
(Don’t forget to change your paths)
Weekly Open Ended Question #6
Mar 3rd
Sorry for the lack of updates this week. I’ve just moved into a new place and I haven’t had time to get anything written up. I’m also lacking ideas lately, so leave some comments if you guys have any requests or ideas.
The answer to the fifth question has been added to the post.
Sixth question:
What is “stuck in active” (SIA), what protocol does it affect and how is it prevented?
Please post answers in the comments (without Googling)!
Answer:
SIA affects EIGRP. It happens when a router queries all of it’s EIGRP neighbors looking for a replacement route and is stuck waiting for replies. Some ways to prevent SIA are to use summary routes and/or stub networks.
Weekly Open Ended Question #5
Feb 26th
This is the fifth question in a series of OEQs. The answer to the fourth question has been added to the post.
Fifth question:
What protocol is used to automatically form trunks on a Cisco switch and how do you disable it?
