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Posts tagged Commands
show ip ospf rib
Mar 3rd
Another quick one. Today I’m going to cover a simple, but very useful OSPF command: “show ip ospf rib”. This command is similar to “show ip route ospf”, but goes a bit deeper.
If you’ve ever done a routing protocol migration, you know how important it can be to see each protocol’s full routing table. Much of the time AD makes this difficult. Administrative Distance (AD) is the believability of a routing protocol on a Cisco device. The default AD values are:
Route Source |
Default Distance |
| Connected Interface | 0 |
| Static Route | 1 |
| EIGRP Summary | 5 |
| eBGP | 20 |
| Internal EIGRP | 90 |
| IGRP | 100 |
| OSPF | 110 |
| IS-IS | 115 |
| RIP | 120 |
| EGP | 140 |
| ODR | 160 |
| External EIGRP | 170 |
| iBGP | 200 |
| Unknown | 255 |
IOS Macros
Aug 16th
Here’s another short (but hopefully useful) post. We’ll be going through IOS Macros.
I’ve never used IOS Macros before, but I was asked about a problem today, and a macro seems to be an ideal solution. A friend of mine is an engineer for a service provider with a very large network. He has been tasked with implementing passive interfaces as the default for OSPF across the network. Most of the devices which will be modified rely on OSPF for management connectivity. When he runs the “passive-interface default” command, he will lose connectivity before he is able to run “no passive-interface [interface]” to restore connectivity. Macros tell the router to run the predetermined commands for us, which will save us from getting locked out.
The topology is simple and not worth a diagram. R1 and R2 are connected via their FastEthernet0/0 interfaces. They are running OSPF on this interface.
BGP Multipath-Relax
May 21st
So I learned a new command today. As usual I want to share with everyone. Today’s command is “bgp bestpath as-path multipath-relax”, which is actually hidden in IOS.
To give some background, BGP will not load balance across multiple paths by default. We can configure it to do so with the “maximum-paths n” command, which is pretty well known. The criteria of this command is that all attributes must match (Weight, LP, AS Path, etc). This is acceptable if we are multihomed to a single AS, but what if we are multihomed to different ASes? In that case we are not able to load balance across theoretically equal paths. Enter the “bgp bestpath as-path multipath-relax” command…
Here’s our first topology:
(click for fullsize)
Now the config:
R1(config)#router bgp 100 R1(config-router)#no synchronization R1(config-router)#neighbor 10.1.12.2 remote-as 200 R1(config-router)#neighbor 10.1.13.3 remote-as 200 R1(config-router)#no auto-summary |
Here we see the basic BGP config on R1. We will only be configuring R1 in this post.
Make IOS Like JUNOS
Mar 24th
Thought you guys would like the title. 
Sorry for the lack of content lately, I’ve been very busy.
Today we’re going to explore the “archive” feature in IOS with a small “archive tutorial”. This was sparked by a recent comment on one of my JUNOS posts. The commenter said that the “archive” command in IOS is the same as “rollback” in JUNOS. They are similar, but “rollback” is there by default where you need to do some tinkering with “archive”. I’ve used it in the past, but never with the intention of mimicking JUNOS’s “rollback”.
Here’s the config:
EDGE(config)#archive EDGE(config-archive)#? Archive configuration commands: default Set a command to its defaults exit Exit from archive configuration mode log Logging commands maximum maximum number of backup copies no Negate a command or set its defaults path path for backups rollback Rollback parameters time-period Period of time in minutes to automatically archive the running-config write-memory Enable automatic backup generation during write memory EDGE(config-archive)#path disk0:config-backup EDGE(config-archive)#max 14 EDGE(config-archive)#write-memory |
To enter the config, we simply type “archive” in global config. There are quite a few options, as we can see. First we’ll need to set our path to store the archived configs, this is a 7200, so I’m using disk0 and a simple naming convention. Next we specify how many configs we want to backup, I’m using the maximum on my device, which is 14. Finally we set the “write-memory” command, which tells the router to archive the config anytime we save.
Useful IOS Commands
Jan 4th
My “Show Run Variations” post sparked an interesting thread on Networking-Forum. I thought it would be nice to make a post with as many useful/little known commands as I can find. I might make a separate page for this depending on how much I can come up with and how frequently updates would be needed. Here we go:
show ip nbar protocol-discovery stats bit-rate top-n 10 |
This command will show you the top 10 protocols (that NBAR can see) on your router. I use this in an alias called “traffic”. You will also need “ip nbar protocol-discovery” enabled on interfaces you want to see statistics for.
show processes cpu sort |
This command will show the sorted CPU usage of all processes running on the router. You could also use “show proc cpu history” to see some ASCII graphs of CPU utilization.
reload in 5 |
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