BGP newbie questions

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May 15th, 2007
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I will be doing my first BGP config from scratch next week and needed some suggestions from the BGP gurus here..

I will have 2x 3640 routers connected to 3 different upstreams. I will call them Platinum, Gold and Silver based on the preference of use.

The Platinum will be the preferred route out and in. The gold would be next and the silver would be last.

See the attached.. Both 3640 routers will run BGP partial routes only (connected networks on the upstreams). They will also run VRRP to provide failover. The switches that handle the upstream coming in will be L2 only and acting as a transciever to the fibre links converting them to copper.

What is the best way to setup BGP to use the Platinum only unless it fails, then the gold and then silver? Minimal traffic over the gold and silver would be allowed, but would prefer to direct 99% of the traffic out to the 1gbps link via Platinum.

The larger switches are 5505 with a single SUP3 and RSM for VLAN termination. They will be running HSRP for redundancy for the server vlans below it (not pictured).

Any suggestions would be appreciated.

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didyap Mon, 05/21/2007 - 10:58
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The best way would be using MED in this case.

rais Mon, 05/21/2007 - 11:01
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Are you going to be connecting to a single AS or different ISPs?


rais Wed, 05/23/2007 - 09:57
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In that case you should consider AS prepending.


sdoremus33 Wed, 05/23/2007 - 16:12
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Yes when you are trying to manipulate routing(egree)from your network AS-Path prepeding is the way to go

paarlberg Wed, 06/06/2007 - 13:34
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I just initiated a BGP session with the first upstream (primary) and none of my routes are being distributed.

Below is my config, IP addresses, pw and ASN info have been removed.

router bgp 99999

bgp router-id

no synchronization

bgp log-neighbor-changes

network our.ip.40.0 mask

network pri.ip.160.199 mask

neighbor pri.ip.225.9 remote-as PRI-ASN

neighbor pri.ip.225.9 password xyz

neighbor sec.ip.95.128 remote-as SEC-ASN

neighbor sec.ip.95.128 password xyz

neighbor ter.ip.130.1 remote-as TER-ASN

neighbor ter.ip.130.1 password xyz

no auto-summary

What am I missing? I know I probably need some filters, etc.. but not sure where to start.


Harold Ritter Wed, 06/06/2007 - 13:52
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  • Cisco Employee,

To advertise your prefixes to your service provider you should either redistribute routes (either from static or IGP) into BGP or use network statements, which match routes that are already present in the RIB.

The recommendation is usually to use a network statement for an Internet connect router.

Hope this helps,

paarlberg Wed, 06/06/2007 - 13:58
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In the above example I am specifying the network for ours and the primary upstream requires that we have a loopback announced for a /32 they provided.

I also only want to receive the minimum routes since it is a 3640 with 128MB of RAM. I have looked and looked and keep finding myself in a loop with the regex portion for lists. The router is now with the basic config posted above.

Any examples would be appreciated..

paarlberg Tue, 06/12/2007 - 05:48
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Ok, my BGP is up and running. I had to null route my ip space and add a prefix list out.

Now that we are talking BGP to our neighbors, I want to set a preference for my outbound traffic. Since our primary is a 1gbps flat rate connection up 100mbps then we are charged a minimal amount. The other 2 are pay as you use links.

I want to set our preferred routes out to be the primary, then the secondary (next least expensive) and then the most expensive.

The next thing is probably answered in my question.. Our primary only allows a single bgp loopback session (we have a single link in from them) and I have 2 routers that are directly connected to it using a 2948G as a media filter/transciever to take the fiber link to copper. Should I set up an iBGP session between my 2 routers so I can get default routes to the primary passed to the second router?


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