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Cisco 3945E Full BGP Table IPv4 and IPv6

I'm looking at Cisco 3945E router to use for our internet edge. Let's say I have two 3945E with 2GB of RAM, and these two are connected to two ISPs with 20-50Mbps of bw and planning to increase it after 3 years.

Network Topology:



1. Receive Full Internet Routing table for IPv4 and IPv6



1. Is 3945E with 2GB of memory enough to handle both IPv4 and IPv6 considering the iBGP connection between two 3945Es.

2. Internet routing table is increasing so fast, is it feasible to use 3945E to handle 20-50Mbps of traffic with Full BGP Table.


Any suggestions is highly appreciated.

Rising star

There is an excellent

There is an excellent document that you can download from, BRKRST-2044 Enterprise Multi-Home Internet Edge Architectures. These figures are from last year but it states the following:

Internet Routing Table size:

IPv4: 451K Routes
IPv6: 12K Routes

Recommended amount of Router DRAM with 2 Internet Feeds: 768MB or More.

Safe for “bgp soft-reconfiguration inbound” and growing IPv4/v6 Tables.

Currently, Full BGP Tables require around 512MB of DRAM.

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I already know this

I already know this information. What I wanted to know is, in real world scenario does 3945E enough to handle this kind of setup, like CEF switching, CPU Load and processing. What is an ideal router to use in ISR G2 platforms?

Not sure if you already got

Not sure if you already got the information you were looking for, but we are running that same setup with 2 3945e's maxed with 2 gig each, and ibgp between the 3945e's


ISP1 100Mbps connection pulling 473K ipv4 routes

ISP2 100Mbps connection pulling 481K ipv4 routes


I have never see the cpu go above 10% unless its rebuilding the full table from an ISP which takes about 1 Minute.  

Memory usage is around 33% used.


We plan on adding ipv6 this fall

VIP Expert

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If your 3945E has sufficient RAM, it should be able to deal with 50 Mbps of traffic with full BGP tables.


Although, you need full BGP tables because?  (Yea, I see you have two ISPs.  But what I found works well is just taking a default from ISPs and using OER/PfR to load share and pick best path.  Remember, each ISP should have reachability to any destination [if they don't OER/PfR will notice and not use that ISP] and fewer AS hops don't really guarantee better perfomance.  [You could also just accept BGP destinations in you ISPs' AS.])


If you need faster router than the 3945E, now there's the 4451-X between it and the ASR1Ks.

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