Loopback and management Network

Answered Question
Apr 28th, 2008
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Hi,


I am trying to create one loopback interface on each network devices in our LAN. For example 192.168.50.1/32 for one device, 192.168.50.2/32 for another device and so on. These ip addresses will be used for management purposes. So the 192.168.50.0/24 will be the management subnet. I am not sure that this is a right approach.

And if the answer is yes, then how can I have proper routing for them to be accessible from all over the network?


Thanks,

Taha

Correct Answer by d.metheny about 9 years 1 month ago

Please be sure to mark this issue as resolved if appropriate. :)

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lamav Mon, 04/28/2008 - 11:40
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Taha, your approach is fine. It is a very common practice to assign /32 addresses to loopback interfaces for management purposes.


Victor


tahalotfi Mon, 04/28/2008 - 12:05
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Thanks Victor,


Is there any sample document that I can take a look at it.I don't know how exactly do it.


Thanks,

Taha

d.metheny Mon, 04/28/2008 - 11:54
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Assuming you're using a dynamic routing protocol, just ensure that the addresses are included in the routing protocol configuration (i.e. network statement in EIGRP, etc.).

tahalotfi Mon, 04/28/2008 - 12:03
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Thanks for your reply.


I don't use routing protocols in the network.

If I use static routes in my network, should I have one route for every device in all other devices? I think it's not a good practice to have so these many static routes for this purpose.


Thanks,

Taha

d.metheny Mon, 04/28/2008 - 12:08
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Personally, I would agree with you - without a routing protocol, you will need to tell each router how to get to every other router's /32 address.


Depending on your network, things could get VERY ugly VERY quickly.

tahalotfi Thu, 05/01/2008 - 05:52
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Hi,

I have few question regarding implementation of a management network with loopbak and EIGRP.

Let's say we have 2 routers.

Router1: loopback1:192.168.149.1/32

Router2: loopback2:192.168.149.2/32


These 2 routers have a point to point L3 connection with 192.168.100.1/30 and 192.168.100.2/30 IP addresses.


How would be EIGRP implementation for just routing management network.


Thanks

d.metheny Thu, 05/01/2008 - 06:04
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1. Create your EIGRP AS (we'll use 1 as an example) on both routers.


2. Turn off auto-summary


3. Add the network statements for the IP's that you want to be advertised. If I am interpreting your comment correctly, you want to advertise ONLY the Loopback IP's.


config t

router eigrp 1

no auto-summary

network 192.168.149.0


This set of commands will work for both routers.


There are many ways to do it, and many variables that can be configured, but this should get you up and going. You can then go to each router and do a and you should see the other router's loopback IP in your routing table, provided you don't have any ACL's in place, and you don't have any pre-existing EIGRP configuration in your routers that would limit/restrict the exchange of EIGRP updates between the routers. If you also wanted to advertise the P2P connections, you could add to the config; that's a matter of preference - I've seen it both ways, and there are pros/cons to doing it.


I typed this quite quickly, so if anyone sees anything I missed/misquoted, please feel free to correct. :)

tahalotfi Thu, 05/01/2008 - 06:16
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I have done exactly the same config, but I can't see the EIGRP route in the routing table. I haven't advertise p2p connections.

d.metheny Thu, 05/01/2008 - 06:21
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How are the routers connected?


Can you attach your configs?

tahalotfi Thu, 05/01/2008 - 06:22
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I advertised the p2p subnet and now is fine. I can see the eigrp routes.


Without advertising the p2p network, I guess I should have static route for them. Am I Right?

d.metheny Thu, 05/01/2008 - 06:27
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DUH - I was just thinking about that, and was getting ready to send you another note. :)


You will need to include the IP's of the interface in order for that interface to advertise EIGRP.


Sorry about that! :(

tahalotfi Thu, 05/01/2008 - 06:38
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I did a test. I remove the p2p network from EIGRP configuration and added 1 static route on each router.


After that I can't see EIGRP routes in the routing table.


By the way routers are directly connected

d.metheny Thu, 05/01/2008 - 06:50
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Yeah - you'll need to include the IP network of the interface(s) in order for that interface to participate in EIGRP.


You could simplify the config by configuring a single network statement of - that would include not only the Loopback interface, but also the connecting IF.

tahalotfi Thu, 05/01/2008 - 06:48
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What's the pros/cons of advertising p2p connections in EIGRP?

d.metheny Thu, 05/01/2008 - 07:19
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Well.....


If you go with the single network statement of 192.168.0.0 (which, by the way, I failed to mention earlier....you may need to include a mask with that statement), so it would look like this.......


network 192.168.0.0 255.255.0.0


due to the fact that without a mask, EIGRP sees this as a Class C network, and assumes a default mask of 255.255.255.0, which would break your EIGRP.


Using the single statement would eliminate the cons of advertising specific P2P links, which are really simply adding more routes to your routing table. However, in a smaller network, that's not necessarily an issue.


Correct Answer
d.metheny Thu, 05/01/2008 - 07:41
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Please be sure to mark this issue as resolved if appropriate. :)

tahalotfi Thu, 05/01/2008 - 07:50
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Thanks very much for your help. I think in your previous post:

"network 192.168.0.0 255.255.0.0 "


should be:

"network 192.168.0.0 0.0.255.255"

d.metheny Thu, 05/01/2008 - 11:58
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I believe I have seen it both ways, with the standard mask or wildcard mask; this may be determined by the IOS version, but I'm not sure.

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