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High Availability for Midsize WAN

I am looking for a High Availability solution for a WAN Core with 12 odd Chanelized and Frac T1 and a handful of odd 56k lines coming into it. Idealy I would like some sort of circuit failover for in the event of a system failure.

I can't seem to be able to find a solution for that meets this requirement. Any and all help is appretiated.


Re: High Availability for Midsize WAN

If I understand you correctly, you are looking for redundant paths to your core facility. If that is right, then you can:

1)_ connect remote sites with each other to get reduandant paths to the core.

2)_ Use other connections, like VPN tunnels over the Internet, to your core site.

3)_ if you are using frame-relay, additional PVCs can prove very practical as well.


New Member

Re: High Availability for Midsize WAN

No that is not what I mean at all.

I am looking for a HA solution. In the IBM AIX world they call it HACMP. In the Microsoft world they call it a Fail Over Cluster.

I have a router with data circuits connected to it. I want a redundant router to 'take over' those data circuits when my primary router fails for whatever reason.

Think of it as a HOT SPARE solution. Instead of a hot spare power supply, a hot spare router. There used to be a technology available for cisco that did this. I find it hard to believe I am the only one looking for this?


Re: High Availability for Midsize WAN

There is a VRRP/Hot Standby Router Protocol supported by Cisco, but that's a LAN protocol. May be that's what you are looking for.

If there are two routers A and B, forming cluster e.g., and router A connects to a T1. If A goes down how will the T1 of downed router A be fed to router B? You are talking additional smart devices here to sense the router down and feed the T1 to other router. I am not aware of any such devices.



Re: High Availability for Midsize WAN

HSRP is the typical way to provide automatic failover for hosts on a LAN with Cisco routers. Other vendors use the open standard VRRP, which provides equivalent services (albeit in a different way with different strengths and weaknesses). WAN links usually are protected by standard routing protocols supporting redundant links and the issues are totally different from those on the LAN side of the routers. Both sides need to be addressed for real high availability.

Chapter six of my book "High Availability Networking with CIsco" is dedicated to the challenge of having one router on a LAN cover for the failure of an alternate router on the same LAN. I would recommend, however, reading the entire book, looking at the concepts in Chapter three (multihoming a host to multiple LANs), Eight (multihoming through multiple ISPs), Nine (redundant firewalls), Eleven (disaster recovery) and Twelve (management considerations).

I am assuming from your clarification that you have already taken care of the cluster and data considerations inherent in a useful HA solution. If you are not familiar with Marcus & Stern's "Blueprints for High Availability", you should pick up a copy and read that first. My book is a 600 page expansion of their one chapter on networking considerations.

For what it's worth, you'll find the data circuits far more prone to failure than the routers at either end. Consequently, while there are black boxes which will switch a data circuit from one router to another, the added availability is more often an illusion, as the black box also becomes yet another single point of failure. You would get more bang for your buck by focusing on physical diversity of your circuits.

Good luck and have fun!

Vincent C Jones

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