Cisco Router for BGP and DS3

Pretty sure a 3745 will do you just fine. I have a very similar scenario at a small DC with a 3845, and run a DS3 and two gig copper connections, and that runs three routing protocols including BGP. It is not an internet router, so perhaps you may want to look into the internet routing table size, but you can always just summarize into a default route if it doesn't cause trouble elsewhere in your network. Your provider should be able to help you there if this is internet facing. In short, bandwidth isn't your issue, the full bgp routing table is where you need to be careful.

This is going to be on the Internet and need the full routing table. I heard for that you need at least 512M of RAM.

M

I cannot validate that requirement, perhaps someone else on the board can. However, it does sound legitimate. 3745's do have a 512 mem option, so you should be fine. I ran some 3600 routers with the full internet table for quite some time in previous employment, so I think the 3700 platform should suffice fine, but I would encourage you to speak with your SE about the mem requirements.

512meg is about right for a full routing table. We have some core routers running on 256 with a full table but it's causing all sorts of problems so I wouldn't start with anything less than 512 now. If you're connecting to two ISP's then using a default route kinda defeats the object so a full routing table is best and gives you the option for selecting the best routes from each ISP.

Good luck.

Chris.

I am thinking of 45mbps to one and 5mbps to other. I hope to set it up to only use the 5mbps in the event the 45 has no route or a really bad route to a destination.

M

A 3745 should be OK, and you will need the 512MB of memory to host the full routing table. The biggest problem is when the line flaps, and you receive the full routing table. The amount of time the CPU runs at 100% is solely dependent of the speed of the processor on router. We use 7206VXR's and with NPE-200's the CPU runs at 100% for about 90 to 180 seconds when the full table is received. NPE-400's reduces this to about 45 second to 90 I have no idea how long this will take on a 3745. You should implement BGP "soft-reconfiguration" to help with CPU load, but this needs to be configured by you ISP as well. If your are purchasing a new router, I would go with a 3825 over a 3745, as it has a faster CPU.

The second issue is your asymmetric bandwidth to the Internet. You do have some control on incoming traffic by prepending your AS multiple times on the low bandwidth link You will probably need to prepend your AS 8 or 9 times maybe more depending on your ISP. For outgoing traffic you will need to use a floating static for your default route to the internet routers.

For outgoing traffic you will need to use

I would suggest simply tagging the incoming routes with a higher local pref on the preferred link.

Chris.

"when the line flaps" what do you mean by that? I assume the interface goes up and down?

Matt