Soft update support is present without "soft-reconfig inbound" but without storing a local copy of the RIB, you *do* have to request a complete table refresh from your peer in order to apply a policy change.
For example, you update a route-map to modify local-preference on some subset of routes. If you just do "clear ip bgp x.x.x.x in" your router will request a route-refresh from the peer and have to actually transfer the table again. Over a T1 or something this can be a big deal. If soft-reconfig is enabled, your router actually cached the provided BGP RIB and when you tell it to "clear ip bgp x.x.x.x soft" it will reprocess the cached RIB but not actually transfer it again. The other reason I still like soft-reconfig is that without it, you can't do "show ip bgp neigh x.x.x.x received-routes" because you don't have a cached, unprocessed copy of the BGP RIB. I like that command for verifying that I did get a specific prefix with such-and-such attributes from my peer before my inbound RMs, prefix-lists, etc., mangled it. I tend to still use "soft-reconfig inbound" if i have the RAM to do so. Bob McCouch CCIE #38296 HerdingPackets.net On Thu, Jan 2, 2014 at 11:12 AM, marc abel <[email protected]> wrote: > You do not need BGP soft-reconfiguration as of IOS 12.0 so that should save > you some memory. > > > http://www.cisco.com/en/US/products/ps6599/products_data_sheet09186a0080087b3a.html > > Previously, in order to perform a soft reset for inbound routing table > updates, the neighbor soft-reconfiguration command directed the Cisco IOS > software in the local BGP router to store all received (inbound) routing > policy updates without modification. This method is memory-intensive and > not recommended unless absolutely necessary. (Outbound updates have never > required the extra memory and are not affected by this feature.) > > With this software release, the BGP Soft Reset Enhancement feature provides > automatic support for dynamic soft reset of inbound BGP routing table > updates that is not dependent upon stored routing table update information. > The new method requires no preconfiguration (as with the neighbor > soft-reconfiguration command) and requires much less memory than the > previous soft reset method for inbound routing table updates. > > > On Thu, Jan 2, 2014 at 9:51 AM, Ryan Jensen <[email protected]> wrote: > > > Morning! > > I have an OT question... > > I have two 40mbps internet connections from the same ISP today, each one > > runs into a 2921 router. I receive a default route via eBGP with ISP and > > the two routers peer via iBGP with each other. I'm going to be dropping > one > > internet connection soon and picking up a second ISP, same bandwidth. > We're > > just doing this to diversify. > > Question is: Would the 2921s have enough resources to accept full > internet > > tables from each ISP? > > The way I look at it, each router would store the BGP table from the ISP, > > and also store the table from its iBGP peer... with soft-reconfiguration > > enabled, It then stores a second copy of each peer's updates. Basically > > requiring the router to store the entire internet BGP table 4 times... > Am I > > looking at this correctly? > > > > I know my current ISP has an option for them to advertise their > originated > > routes (core routes) and a default, so that would significantly decrease > > the update size from that peer, but I don't know if my incoming ISP has > > that option. > > > > Routers are default hardware spec, 1g RAM, 256mb Flash > > IOS 15.2(4)M3 > > > > Thoughts?? > > _______________________________________________ > > Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: > > > > iPexpert on YouTube: www.youtube.com/ipexpertinc > > > > > > -- > Marc Abel > CCIE #35470 > (Routing and Switching) > _______________________________________________ > Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: > > iPexpert on YouTube: www.youtube.com/ipexpertinc > _______________________________________________ Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: iPexpert on YouTube: www.youtube.com/ipexpertinc
