Router To Hold all BGP IPv4/IPv6 routes

[Elopower123]

Hi,

I'm looking to upgrade my company's edge router to a router that can actually process all the BGP IPv4 and IPv6 routes coming from our ISP and exchange point because right now we are only receiving default routes. I'm currently considering CISCO ISR 4331 because I've looked at the specs and I feel that the memory capacity of 4GB should be able to handle the routing. So I would just like other opinions about this; if this is ok or if I need to get another(higher) router.

Also I would like if anyone can confirm the VPN routing capabilities of the router.

Thanks for your time.

[Giuseppe Larosa]

Hello @Elopower123 ,

an ASR 1000 with 16GB memory would be far better.

check if the ISR 4331 memory can be upgraded to 8 GB.

4GB RAM may be not enough for your purposes as the number of IPv4 routes in a full table is in the order of 800,000 routes.

You need to consider if you want to multihome in the future, the router needs to receive and store two BGP full tables.

Hope to help

Giuseppe

[Elopower123]

Hello Larosa,

The memory is upgradeable to 16GB. But then I also looked at the 4431 and 4461, they have an onboard DRAM of 6Gb and 12GB respectively when the combine the data plane and control plane DRAM. Perhaps one of these might serve better.

Also do I need to get any licenses in order to achieve full routing capabilities as well as IPSEC VPN on these routers?

[Giuseppe Larosa]

Hello @Elopower123 ,

>> Also do I need to get any licenses in order to achieve full routing capabilities as well as IPSEC VPN on these routers?

I don't think you need additional licenses but the device should be considered dedicated to this job BGP peering, so you should put your IPSec VPN on another box.

It is not only important the amount of RAM but also the CPU should be powerful enough to handle the initial loading of BGP tables and to be able to support the BGP scanner process (that is executed every 60 seconds) as mentioned by Joseph.

The suggestion by BB to deploy two routers given this type of routers is also interesting and it should be considered.

As I have mentioned in my first post I have seen customers using a pair of ASR 1000 with 16 GB of RAM for this job regardless of link speeds with good results.

Two ISR 4461 might be a good choice if you are sure that you don't need to increase the link speed in the mid term.

Hope to help

Giuseppe

Hope to help

Giuseppe

[Elopower123]

Hi Larosa,

My link is actually an STM1 link and we might be upgrading in the middle term. So I'm guessing that the 4331 would not be able to handle that.

We are currently using a 2901, if I upgraded the ram to say 2.5GB would it be able to take the BGP routes? Since it's default throughput is up to 1GB unlike the 4331 which is software limited.

[Elopower123]

Also can you guide me on how I can upgrade the 4000 series routers to get the full bandwidth capacity and where I can get the pricing for the licenses

[balaji.bandi]

as per my knowledge 1GB hold around 700K routes, if you have 8GB is good to have good performance for other activity.

check maximum ram you can do as per below :

https://community.cisco.com/t5/routing/cisco-isr-4431-full-bgp-ipv4-ipv6-routes/td-p/2865871

[Elopower123]

Hello @balaji.bandi 

Cisco documentation says that you can upgrade to 16GB, though I would rather get something that can serve my needs with its default hardware and then upgrade in the future if need be.

[balaji.bandi]

Is this single router deployment or Dual routers ?

if single router i suggest to go with 8GB RAM and still consume more you can upgrade more to 16GB (not rquired in case)

if you have dual Router deployment, you can go with basic and see the performance and usage, you get ability one device at a time.

single device deployment you need more downtimes, which eliminates downtimes when you deploy high availability

[Joseph W. Doherty]

For a very different opinion . . .

Years ago, I was in a situation where I had 3660s connected to two different ISPs, and using default routes to both.

In theory, of course, although we had the expected 50/50 outbound traffic split, we were not using the "optimal" path to destinations.  So, we migrated to accepting full Internet tables from both providers.  Ah, then, destination traffic chose the "shortest" AS path, except in cases where the two providers had equal AS paths, then we still split the traffic 50/50.

We found the (two) full Internet tables really loaded down the CPU performance of the routers.  We had the RAM, but what was taking up much of the router's CPU was the BGP scanner.  Of course, a 4K ISR likely has a more powerful CPU, but then the Internet route table has grown.  Further, at that time we were only doing IPv4, but you want IPv4 and IPv6.

In any case, when I thought about it, what did the "shortest" AS path, to a destination really mean?  What's the capacity of the links along one ISP's path vs. the other, and further, how "loaded" are those links?

Also at that time, Cisco recently released a new technology, OER (optimal edge routing, now PfR, performance routing), actually "aimed" at Internet edge connections.

This technology can load balance egress links, dynamically, and/or shift flows if one path is better performing (although worse from a routing metrics perspective).  It could do this using any Internet sized route table, from full, to partial, to just default.

So, I went back to using just two defaults, with their default 50/50 split, and allowed OER to shift flows to balance the two egress links and/or shift flows if it detected, for a particular destination, if the "worse" path was actually a better performing path.

Besides now obtaining dynamic "optimal" egress traffic routing, the CPU load on the routers much decreased, along with a huge reduction in memory usage too.  I was very pleased with how OER performed.

Don't recall if OER had this feature too, the initial PfR also could "influence" ingress link loading too, although much more complicated to setup.  (PfR also allowed QoS to also weigh in to how egress traffic should be shifted.)

If you do consider PfR, I believe it now requires its own feature license, on later routers.

Possible not germane to this, but I also believe PfR may have been the forerunner, and/or component, of Cisco SD-WAN technology.