Routing Table update upon server not being available

[a-greaves]

We have a router connecting to a client router over a serial line, which then connects through a single Firewall to a client server.

If the ethernet on the farside of the firewall were to fail the 2 routers wouldn't know the server was no longer available.

Is it possible for a Router to monitor the server - say via 'FTP Get' through the Firewall and if server becomes unavailbale, to update its Routing Protocol accordingly, so our Router can use alternative route.

AndyG

[rais]

How will you network reach the server through alternate route if the server network is down?

Router cannot monitor the server via FTP.

Unix OS supports RIP and OSPF to dynamically learn alternate routes.

Thanks.

[a-greaves]

we'd hope the router in question could update its routing table to inform another router of ours that the subnet the server was on was unavailable. This other router would then either use a floating static or routing protocol to point to yet another router for a less preferred route.

AndyG

[vcjones]

You have several potential approaches here:

1 - Cisco has announced the ability to use ping to control routes (to compete with Nexland and other DSL oriented routers). You would need to check the feature navigator to see if this new feature has made it into an IOS release which runs on your platform.

2 - Use a Nexland Pro 800 Turbo or equivalent router which has the ability to select routes based on the ability to ping (both ICMP and HTTP) a destinatlion address.

3 - Run BGP between your router and the server (requires running gated or the equivalent on the server). BGP can be safely used through firewalls, see the white paper on "Redundant Firewalls" on my web site.

4 - Set up the server with multiple interfaces on multiple LANs with full routing to a single loopback address on the server. Propagate that address through all available paths using conventional routing protocols. See Chapter 3 of my book "High Availability Networking with Cisco" for examples.

Note that if the firewall is configured to ONLY let through FTP, all of these approaches will require support from the firewall administrator to open up the appropriate protocols through the firewall.

Good luck and have fun!

Vincent C Jones

www.networkingunlimited.com