[c-nsp] Best practice - Core vs Access Router

Sergey Nikitin oldnick at oldnick.ru
Tue Feb 9 06:15:15 EST 2010

May be you should try to find out what is the reason of the packet loss? 
  Is there a high CPU load? Do you have control-plane configured? Do you 
have traffic congestion? May be you don't really need to redesing you 

Andy B. wrote:
> I am running one 6509 as a core router:
> IOS: SXF15a
> 1x WS-SUP720-3BXL
> 1x WS-X6748-GE-TX
> 2x WS-X6704-10GE
> On this core I am doing BGP with 2 upstreams (full BGP table IN) and
> 10 downstreams (full BGP table OUT).
> I am also doing OSPF with 4 other core routers in this AS.
> On top of that there is one VLAN on this core that serves as a default
> gateway for approximatively 5000 servers, producing around 30 GBps
> outbound traffic and 10 GBps inbound.
> Recently I noticed that this core router becomes very unresponsive
> from time to time, dropping OSPF and BGP sessions (hold time expired
> and so on). SNMP generated stats become useless as well, because most
> SNMP requests to that core are timing out. It's really just the core
> that is rather slow, but reachability to my customers and from my
> customers to the internet remains perfect. Pinging the loopback
> interface of the core or any default gateway IP address of the busy
> VLAN can show up to 60% packet loss
> Therefore I was thinking to split the core and move this very active
> VLAN to a different router behind the core and only add a static route
> to the core, so that the new router can handle these many MAC
> addresses and hopefully get my core more responsive again.
> Does this scenario make any sense at all? Is it wise to have one core
> router with many transit (in and out) BGP sessions also act as an
> access router / default gateway for several thousand servers? What is
> usually the best practice here?
> Thank you for your clues.
> Andy
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