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Posts tagged Certification
OSPF Area Types: Totally Stubby
Jun 6th
This is the first post in a series about OSPF Area Types. Today we’ll go over Totally Stubby areas. We’ll be using the same topology as the Stub post. I’m also reposting the first portion of that here since it will be the same.
Quick refresher, OSPF Totally Stubby Areas allow only intra-area routes and a default route generated by the ABR (Type 2 LSAs – the default route comes through as a Type 3 LSA, but no other Type 3s are allowed). Inter-area and External routes (Type 5 LSAs) are not allowed in totally stubby areas.
(For more detailed information on LSAs and Area Types, check out this post.)
Here’s the topology:
OSPF Area Types: Stub
Jun 4th
This is the first post in a series about OSPF Area Types. Today we’ll go over Stub areas. This one will be somewhat short on config, but should have a good amount of show commands.
Quick refresher, OSPF Stub Areas allow inter- and intra-area routes (Type 2 and Type 3 LSAs). External routes (Type 5 LSAs) are not allowed in stub areas.
(For more detailed information on LSAs and Area Types, check out this post.)
We’ll be using the same topology we used for OSPF Authentication:
I’m not going through the basic OSPF config, so assume everything is configured as the diagram suggests. I’ve also redistributed loopbacks on each router to give us some external routes, and I added 34.34.34.34/32 to Area 34 so we have an intra-area route to look at. Let’s look at some show commands BEFORE we make area 34 a stub:
OSPF Authentication
Jun 1st
This post is about the different OSPF authentication methods. It will be part of a series outlining OSPF commands/technologies.
We can configure OSPF to use authentication for an entire area, or just for a single interface. Today we’ll go over both. Here’s the topology:
First we’ll setup authentication for all of area 0:
R1(config)#interface FastEthernet0/0 R1(config-if)#ip ospf message-digest-key 1 md5 cisco R1(config-if)#ip ospf 100 area 0 R1(config-if)# R1(config-if)#router ospf 100 R1(config-router)#area 0 authentication message-digest R2(config)#interface FastEthernet0/0 R2(config-if)#ip ospf message-digest-key 1 md5 cisco R2(config-if)#ip ospf 100 area 0 R2(config-if)# R2(config-if)#router ospf 100 R2(config-router)#area 0 authentication message-digest R3(config)#interface FastEthernet0/0 R3(config-if)#ip ospf message-digest-key 1 md5 cisco R3(config-if)#ip ospf 100 area 0 R3(config-if)# R3(config-if)#router ospf 100 R3(config-router)#area 0 authentication message-digest |
Nothing crazy here, we configure OSPF and an MD5 key under our area 0 interfaces, then we specify that all of area 0 should use MD5 authentication. Note that the commands differ slightly if we want to use clear-text, it would be “ip ospf authentication-key [key]” and “area 0 authentication” under the OSPF 100 process.
Let’s verify:
R1#sh ip ospf neigh
Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 1 FULL/DR 00:00:32 10.1.123.2 FastEthernet0/0
3.3.3.3 1 FULL/DROTHER 00:00:35 10.1.123.3 FastEthernet0/0
R1#sh ip ospf int fa0/0
...
Message digest authentication enabled
Youngest key id is 1 |
Everything is working, our neighbors are up and we see that authentication is enabled with the key we specifcied. Note, if we leave off a key, the neigbhors will still form and MD5 will still be enabled, but it will say key 0:
OSPF Lab #2 Tasks
May 19th
This is the second OSPF post I’ll be doing for CCIE lab preparation. Today I’m posting the tasks, then tomorrow or the day after (or possibly after the weekend, depending how busy I am) I’ll post the walkthrough. If any of you work on this before the walkthrough, leave a comment.
Here’s the topology:
(Click image for fullsize)
Click here for the initial configs
Here are the tasks:
1. Configure R1, R2 and R3′s S0/0 interfaces in Area 0. Ensure that DR and BDR are elected. Advertise all loopback0s on all routers into OSPF.
2. Configure R1 as the default gateway for all OSPF routers. Do not use the “default-information” command.
3. Configure R6 to use the path through R4 to get to area 0 Do not use any interface level commands to accomplish this.
4. Configure R4 to filter any type 3, 4, 5 and 7 LSAs from entering area 45.
Quick BGP Challenge #1
May 12th
This is the first little challenge I’m posting on here. If you frequent the forums, you likely saw the one I had for OSPF. I thought of another challenge while talking to a buddy. Here’s the topology:
Make R1 prefer the path through R3 for the 192.168.1.0/24 network. The configuration must be on R1. Do not use Weight or Local Preference to accomplish this. Assume that all previous configuration is correct.
This one is a little different than the OSPF challenge in that there are many ways to accomplish it. I’ve thought of a few, I want to see what everyone else comes up with.
Go!
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