Hello all,
I’m sure you’ve heard this one before – but my searches aren’t coming up with anything. It’s a basic question that I’d like to be sure about before going further -- certainly would appreciate any help.
I’m trying to design a failover scheme for a site-to-site vpn in the simplest way – i.e. using an interior routing protocol on the gateway router, instead of BGP, if possible. The basic question is about how interior routing protocols work. I know that they will advertise directly connected subnets. The question is, what determines whether that subnet has ‘failed’?
To illustrate the problem, if I have stub networks at SiteA and SiteB connected over a WAN, both configured for EIGRP, and the network 172.16.30.0 out E0 on SiteB has only one PC connected to it, what will make EIGRP at SiteB conclude that 172.16.30.0 has failed? Must it be the E0 interface itself that has failed? Or can it be the Ethernet cable or NIC on the connected PC?
My guess is that only a malfunction of the router’s E0 interface will cause EIGRP to conclude that the subnet is ‘down’. Because even if the cable and connected PC NIC fails, the router E0 address itself is still in the subnet. So technically, the subnet can still be reached, and EIGRP will advertise this. But I’m not sure.
If the above is true, then my plan to use EIGRP, etc. on the gateway router is foiled. My hope has been to perhaps avoid getting the ISP routers involved at all – instead, just have our own gateway router (terminating a T1, etc.) advertise to others on the inside that it’s directly connected link to the ISP is down, not necessarily because its interface has gone bad, but also when something at the ISP side has gone down. Then, with this information, another interior router can use a floating static route, etc. to direct traffic to a failover Internet link.
Is this off the wall, or is something like BGP the only answer? Thank you very much for any help you can provide.
I’m sure you’ve heard this one before – but my searches aren’t coming up with anything. It’s a basic question that I’d like to be sure about before going further -- certainly would appreciate any help.
I’m trying to design a failover scheme for a site-to-site vpn in the simplest way – i.e. using an interior routing protocol on the gateway router, instead of BGP, if possible. The basic question is about how interior routing protocols work. I know that they will advertise directly connected subnets. The question is, what determines whether that subnet has ‘failed’?
To illustrate the problem, if I have stub networks at SiteA and SiteB connected over a WAN, both configured for EIGRP, and the network 172.16.30.0 out E0 on SiteB has only one PC connected to it, what will make EIGRP at SiteB conclude that 172.16.30.0 has failed? Must it be the E0 interface itself that has failed? Or can it be the Ethernet cable or NIC on the connected PC?
My guess is that only a malfunction of the router’s E0 interface will cause EIGRP to conclude that the subnet is ‘down’. Because even if the cable and connected PC NIC fails, the router E0 address itself is still in the subnet. So technically, the subnet can still be reached, and EIGRP will advertise this. But I’m not sure.
If the above is true, then my plan to use EIGRP, etc. on the gateway router is foiled. My hope has been to perhaps avoid getting the ISP routers involved at all – instead, just have our own gateway router (terminating a T1, etc.) advertise to others on the inside that it’s directly connected link to the ISP is down, not necessarily because its interface has gone bad, but also when something at the ISP side has gone down. Then, with this information, another interior router can use a floating static route, etc. to direct traffic to a failover Internet link.
Is this off the wall, or is something like BGP the only answer? Thank you very much for any help you can provide.