We have 2 Cisco 3750's (EMI) in stackwise configuration. We have 2 Cisco 7204 VXR's each connected to a different 3750 and externally to multiple ISP's running BGP. We have multiple racks - each rack has a 10/100 switch (public lan) usually HP Procurve 2626 and a Gigabit switch (Private Lan) usually HP Procurve 2824. Switches are connected to alternate Ciscos and will be running MSTP to create a redundant ring to each rack (not configured yet though..).
All clients are in private vlans and have their gateway interface on the Cisco 3750 stack. The routers have static routes for each subnet pointing towards the 3750 and a null route to drop all other traffic on unused subnets. The Cisco 3750 stack has a default route to a HSRP IP floating between the two routers.
The HSRP floating IP method means that one router gets all the traffic and then sends traffic over to the other if that route is more preferable. Obviously this isn't a fantastic design and will give us problems when we get nearer to the interface speeds.
My proposal to fix this is to redistribute some of the BGP table into OSPF and run OSPF on the 3750 Stack so the 3750 can make a more educated choice in its routing decision. In O'Reilly "BGP" book it gives an example of this as follows:-
(should restrict to only match routes with an AS Path of up to 4 ASes in it)
router ospf 3
redistribute bgp 60055 subnets route-map LIMITRED
default-information originate metric 20
network 192.0.2.0 0.0.0.255 area 0
!
ip as-path access-list 23 permit .+_.+_.+_.+
!
access-list 33 permit 192.0.254.17
!
route-map LIMITRED deny 10
match as-path 23
!
route-map LIMITRED permit 20
match ip next-hop 33
!
Questions:
1) Any disadvantages to doing this?
2) Could I achieve the same by extending iBGP to also run on the 3750 and applying a similar as-path filter as above to keep the BGP table from filling up the available memory?
Which would be less resource intensive etc?
If this is a better direction then would it be better to filter the BGP table being advertised from the cisco routers as well as filtering incoming on the 3750 to reduce the resources taken to apply the filter on each update?
