[c-nsp] Monitoring ethernet circuits with GRE

[David Prall]

You'll need to enable tunnel keepalives for the interface to actually go
down if the route to the destination stays present. Another option for
Ethernet interfaces is to monitor the routing protocol instead.

David

--
David C Prall dcp at dcptech.com http://dcp.dcptech.com
  

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net 
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of William
> Sent: Tuesday, November 28, 2006 10:03 AM
> To: [c-nsp]
> Subject: [c-nsp] Monitoring ethernet circuits with GRE
> 
> Hi list,
> 
> With the increasing amount of Ethernet circuits being used within our
> business I'm looking for a simple way to monitor the links. As we all
> know, most of the time the WAN interface will be up/up even if there
> is a problem in the 'cloud' it uses to get to the other end point.
> 
> I've been looking into using a simple GRE tunnel from one end to the
> other, if there is a serious amount of packet loss on the link and the
> tunnel goes up/down I can use one of our systems to alert us.
> 
> Config goes like this:
> 
> interface Tunnel1
>  no ip address
>  tunnel source 1.1.1.1
>  tunnel destination 1.1.1.2
> 
> 
> With the last two lines reversed for the other side, everything should
> come up and just *work*
> 
> I'm currently testing this with a 2600 and 3550, the port on the 3550
> is routed and has an ip address applied to it.
> 
> My problem consists of the tunnel being up/up, and sometimes just
> being down. Having to issue a shut+no shut on either interface to
> bring the tunnel back up. Sometimes the 3550 is reporting the tunnel
> is up when the 2600 isn't contactable over IP!! (having shut down the
> interface on the 2600)
> 
> Am I running into silly issues because the 3550 isn't capable of GRE?
> Most of the networks I'm currently looking after consist of L3 3750's
> with routed ports to connect to WANs. Just need some guidance if I'm
> doing something wrong or if the hardware I'm dealing with just cant do
> it!
> 
> Thank you for your time.
> 
> William
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