[nsp] gre tunnel using loopback for source

[Eric Richard Knudson III]

Pete,

Yeah, gre tunnels don't reflect an accurate status, I think I've seen
them come up as soon as a valid source address was configured. You'll
need gre keepalives to provide a mechanism to change the interface
status:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft
/122t/122t8/grekpliv.htm

Eric


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Pete Templin
Sent: Monday, June 02, 2003 4:29 PM
To: Joshua Sahala; cisco-nsp at puck.nether.net
Subject: RE: [nsp] gre tunnel using loopback for source


I've got ten tunnels in a full mesh between five sites, all using the
loopback as the source and the destination.

On IOS 12.2(16), I did notice (but didn't investigate further; didn't
have an easy way to build a test network due to overlapping VLAN
identifiers) that the tunnel would show a status of up/up as soon as a
valid route was created to the destination, even if the far end router
was non-existent.  Might have been a random goof on my part; but might
be more important in other topologies.

Pete Templin
IP Network Engineer
Tex-Link Communications
pete.templin at texlink.com
(210) 892-4183

-----Original Message-----
From: Joshua Sahala [mailto:joshua.ej.smith at usa.net]
Sent: Monday, June 02, 2003 3:52 PM
To: cisco-nsp at puck.nether.net
Subject: [nsp] gre tunnel using loopback for source

hello all,

i was wondering if it is possible to get a gre tunnel to work using a
loopback for the tunnel source.  i have three interfaces (traffic is
moved from one to another by local preference) that could potentially be
the active interface, so i am trying to get a tunnel that will stay up
if i move the traffic off the interface. bgp will come up, and addresses
in lan2 can ping my router, but not any devices in lan 1, and lan1
devices cannot ping the r2 loopback, or any lan2 devices


lan1
 |
r1
 |
r2
 |
lan2

r1 config:
interface Tunnel17
 description connected_to_test
 ip unnumbered Loopback19
 no ip directed-broadcast
 ip mtu 1580
 tunnel source 192.168.1.194
 tunnel destination 10.10.1.42

interface Loopback19
 ip address 192.168.1.194 255.255.255.255
 no ip redirects
 no ip unreachables
 no ip directed-broadcast
 no ip proxy-arp

router bgp 65056
network 192.168.1.0 mask 255.255.255.0
neigh 172.16.16.1 remote as 65145

ip route 172.16.16.1 255.255.255.255 tun17


r2 config

interface Tunnel1
 description connected_to_test
 ip unnumbered Loopback9
 no ip directed-broadcast
 ip mtu 1580
 tunnel source 10.10.1.42
 tunnel destination 192.168.1.194

interface Loopback9
 ip address 172.16.16.1 255.255.255.255
 no ip redirects
 no ip unreachables
 no ip directed-broadcast
 no ip proxy-arp

router bgp 65145
network 172.16.16.0 255.255.255.0
neigh 192.168.1.194 remote as 65056

ip route 192.168.1.194 255.255.255.255 tun1
ip route 192.168.1.19 255.255.255.255 fas1/1

int fas1/1
ip address 10.10.1.42 255.255.255.252

thanks

/joshua


"Walk with me through the Universe,
 And along the way see how all of us are Connected.
 Feast the eyes of your Soul,
 On the Love that abounds.
 In all places at once, seemingly endless,
 Like your own existence."
     - Stephen Hawking -



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