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Colby
Colby Glass has been in IT since 2002. He is currently a network engineer with a large Cisco partner and holds the CCNP, CCDP, CCIP, CCNA: Voice, CCNA, JNCIA-ER and ITILv3: Foundations certifications. He has also passed the CCIE R&S Written exam and is studying for the Lab exam.
Posts by Colby
OSPF Area Types: NSSA
Jun 15th
Today we’ll go over Not So Stubby Areas (NSSA). We will be using a slightly different topology here, we will make R4 an ASBR with a connection to the internet.
Quick refresher, OSPF NSSAs have inter and intra-area routes (Type 2 and Type 3 LSAs) and also external routes in the form of Type 7 LSAs, which are converted to Type 5 LSAs by the ABR.
(For more detailed information on LSAs and Area Types, check out this post.)
Here’s the topology:
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 (“redistribute connected subnets” under the OSPF process) 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. I’ve also added a static default route on R4 which I’m injecting into OSPF with the “default-information originate” command. Let’s look at some show commands BEFORE we make area 34 an NSSA:
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:
Cisco Port to ASIC Mapping
May 31st
You know you’re a nerd or really bored when you get into conversations about the oversubscription of ports on each ASIC. 
So obviously I was having this conversation, lol. I’m pretty noobish when it comes to the mechanics of network gear. I know the configuration relatively well, but not enough about the internals. So I did some searching and came across this great page on James Ventre’s blog. Check it out if you’re curious about ASICs and how many ports each will support on various platforms. I found some other interesting reading on the site as well.
Here’s another helpful link describing the architecture of the 3750-Es. Page 53 goes into the ASICs specifically.
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