On Tue, 8 Apr 2008, Uddin, Tahir wrote: > BTW, Mark, what is the lowest you would go within the CORE and the > lowest on the customer WAN link and are there any resource issues > (memory, cpu) that are of concern.
That depends on many variables. One of the things the hold timers were designed to do is provide a small time buffer between the loss of IP connectivity that would take a BGP session down and the actual tear-down of that session. Setting it too low can thrash the CPU on your router if you have an unstable link or some other issue introduces instability into your backbone. I have one private network interconnected to my backbone that has BGP hold timers set to 15 seconds with a 5 second keepalive. All of the links are local (in buildings on my campus), all of the routers are managed by me and are exchanging a very small number of prefixes (<5). OSPF was not practical or possible for several reasons. I would not do this with customers, especially customers who are announcing/ receiving more than a handful of prefixes, because the potential for customer-induced instability to hit the CPU on my PE routers and possible elsewhere is too high. If you choose to do this, make sure you have safeguards in place, such as appropriately tuned flap damping, and an appropriate limit on the number of prefixes you will announce or accept over the BGP session. jms _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
