I have a network with two upstreams that land in datacenters many miles
apart. The hardware involved is Cisco 7507s with RSP4s and VIP4-80. I've got
a curious problem which I hope others here have faced.
A while ago we got a /28 from each provider and attached it to a
dedicated fast ethernet interface at each location. Inbound traffic arrives
normally and anything arriving on that port is policy routed to the upstream
that provided the prefix.
This was all well and good when it was a little firewall with a Linux
machine behind it being used to check latency and do other diagnostics, but
the sales people noticed it and have lined up a couple of opportunities to
sell a service that would depend on our being able to receive and send
traffic from blocks less than a /24.
The policy routing works fine at low volume, but the RSP4 is rated to
only do four megabits and I know they're going to exceed that.
I can terminate this subnet on another router, wire that device into the
7507 with a crossover, and establish a BGP session. I'm wondering if there
is a tidy way to set next hop in some fashion using route-maps such that all
the marking would be done on the auxillary machine and the traffic passing
through the 7507 would be CEF switched rather than process switched.
Neal,
If your providers are doing uRPF, and it is always the case that hosts using
provider A's IPs must route through provider A, and hosts using provider B's
IPs must route through provider B, then why not enforce this behavior in your
routing tables rather than doing PBR?
From your description, it doesn't sound like you're distributing subnets
across datacenters, and it's difficult to tell how, why, or if you're sharing
provider routes between your routers.
Stephen Kratzer
Network Engineer
CTI Networks, Inc.
I have a network with two upstreams that land in datacenters many miles
apart. The hardware involved is Cisco 7507s with RSP4s and VIP4-80. I've got
a curious problem which I hope others here have faced.
[snip]
I can terminate this subnet on another router, wire that device into the
7507 with a crossover, and establish a BGP session. I'm wondering if there
is a tidy way to set next hop in some fashion using route-maps such that all
the marking would be done on the auxillary machine and the traffic passing
through the 7507 would be CEF switched rather than process switched.
I hope the NANOG list can forgive me replying--I have a soft spot for 7500's.
A few things to check on your box before giving up:
-if you don't need v6 or mpls, run the most recent 12.0S code
available - cef-switched policy based routing (which I'm not convinced
is required to do what you describe) has been part of 12.0 feature set
since its inception. Weather it works or not due to regressions is
another story.
http://www.cisco.com/en/US/docs/ios/12_0/qos/configuration/guide/qcpolicy.html
-12.4 main works well enough, adds mpls p/pe and ipv6 in cef
-"ip cef distributed" (make sure it's enabled, regardless of the IOS version)
Another suggestion is to place customers into their own unique
interface (i.e. sub-interface vlan, etc), and simply bind this
customer to a VRF corresponding to the provider they expect/wish/etc
to egress.
-tk