[j-nsp] Junos ospf question

R S dim0sal at hotmail.com
Wed Sep 25 05:42:47 EDT 2013

indeed I make it simpler....

- network is already running with ospf (very sensite traffic)
- the concept is A-C-B-A as you correctly understood, but there are between A and B 4 links with 4 big MXs on each side and on C there are two different big SRX, hence topology is not so easier
- traffic is OSPF over IPSEC on each link
- the idea is to find a solution under the current config/topology/routing domain, otherwise if I was enabled to rebuild everything I'd do in different way...

Subject: Re: [j-nsp] Junos ospf question
From: p1 at westerlund.se
Date: Wed, 25 Sep 2013 11:32:01 +0200
CC: ipv6freely at gmail.com; juniper-nsp at puck.nether.net
To: dim0sal at hotmail.com

First let me see if I understand you correctly by rephrasing.
- Three sites A, B och C all connected with direct links- Link A-B has high capacity- Links A-C and B-C has lower capacity- High volume storage traffic traverses link A-B and must not use links A-C or B-C, even if link A-B goes down- There is also other low-volume traffic between all sites that should be routed around possible broken links.
Why not first try to solve it the easy way instead of using routing magic?
- If the high-volume storage traffic has static addressing that is unique, you can use static routes that are NOT exported into OSPF.
If the easy way does not apply, there is a slightly more complex way to do it:
- If you can classify storage traffic statically with a filter, use FBF to direct that traffic to a static default route in another routing instance.
I don't really recommend it, but there are high-tech alternatives that do about the same as FBF in this case, but in a more "interesting" way. Usually you should always think KISS in production, but I must mention it: Multitopology routing.
With MT routing one OSPF instance can have more than one topology active, in this case one with only A and B present, and another where all of A, B and C are present. You then classify the ingress traffic and assign it to one of the topologies (by using their specific routing/forwarding table).
Here is a link to where you can get started: http://www.juniper.net/techpubs/en_US/junos12.1/topics/usage-guidelines/routing-configuring-multitopology-routing-in-ospf.html .
Remember: I don't recommend it!
25 sep 2013 kl. 10:39 skrev R S <dim0sal at hotmail.com>:basically I've a triangulation A - B - C - A

single area 0

A-B link is 10Gbs
A-C and B-C is 1 Gbs

since in A-B run a very high volume of traffic (storage), I do not want if A-B fails this traffic goes through C

C redistribute as well statics into OSPF

Hope it clear now


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