From: SFeldberg@xxxxxxxxxxxxx
Date: Thu Aug 16 2001 - 19:20:02 GMT-3
Group,
This is my first "real" post, I have read the archives regarding this
subject. My understanding of this issue is that tunnel "flapping" can be
caused by the dynamic routing protocol trying to reach the tunnel
destination address via the tunnel itself. That being said...
I am using EIGRP in my scenario with three routers, in a small
hub-and-spoke configuration. It is actually part of a larger configuration
(Fatkid 325) where the tunnel was created as a substitute for the BRI
connection that is not available. R3 is connected to R4 via serial, R2 is
connected to R4 via ethernet. The tunnel sources and destinations are
Loopback interfaces on R2 and R3. The tunnel interfaces themselves are
using a /28 subnet of the default network for the exercise.
I have read postings that have suggested using a distribute-list to
accomplish the filtering of the updates that cause recursive routing. I
tried this approach, but I was not able to get it to work. I then thought,
what if I make the metrics of the tunnel so bad that EIGRP would not see
the tunnel as a preferable option? Doing this, I have achieved the
objective of keeping the tunnel up while neighbor relationships are formed
while having all routes advertised through the tunnel.
I have questions about the "gotchas" I will encounter in this scenario, and
I would appreciate feedback from anyone who can provide me with alternative
methods (no passive-interface solutions please).
R3
interface Loopback0
ip address 190.19.15.185 255.255.255.240
no ip directed-broadcast
!
interface Tunnel0
bandwidth 1
ip address 190.19.15.135 255.255.255.240
no ip directed-broadcast
delay 10000
tunnel source Loopback0
tunnel destination 190.19.15.151
!
interface Serial0
bandwidth 4000
ip address 190.19.15.5 255.255.255.192
no ip directed-broadcast
no ip mroute-cache
!
router eigrp 1
network 190.19.0.0
R3#sh ip eig n
IP-EIGRP neighbors for process 1
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
1 190.19.15.131 Tu0 10 00:28:12 0 3000 0 7330
0 190.19.15.4 Se0 13 00:29:18 39 234 0 9126
R3#sh ip rou
190.19.0.0/16 is variably subnetted, 6 subnets, 2 masks
D 190.19.15.160/28 [90/1280000] via 190.19.15.4, Serial0
C 190.19.15.176/28 is directly connected, Loopback0
C 190.19.15.128/28 is directly connected, Tunnel0
D 190.19.15.144/28 [90/1305600] via 190.19.15.4, Serial0
C 190.19.15.0/26 is directly connected, Serial0
D 190.19.15.64/26 [90/1177600] via 190.19.15.4, Serial0
R3#sh ip eig to
IP-EIGRP Topology Table for AS(1)/ID(190.19.15.185)
P 190.19.15.160/28, 1 successors, FD is 1280000
via 190.19.15.4 (1280000/128256), Serial0
via 190.19.15.131 (2562713600/793600), Tunnel0
P 190.19.15.176/28, 1 successors, FD is 128256
via Connected, Loopback0
P 190.19.15.128/28, 1 successors, FD is 2562560000
via Connected, Tunnel0
P 190.19.15.144/28, 1 successors, FD is 1305600
via 190.19.15.4 (1305600/409600), Serial0
via 190.19.15.131 (2562688000/128256), Tunnel0
P 190.19.15.0/26, 1 successors, FD is 551936
via Connected, Serial0
P 190.19.15.64/26, 1 successors, FD is 1177600
via 190.19.15.4 (1177600/281600), Serial0
via 190.19.15.131 (2562585600/665600), Tunnel0
R2
interface Loopback0
ip address 190.19.15.151 255.255.255.240
no ip directed-broadcast
!
interface Tunnel0
bandwidth 1
ip address 190.19.15.131 255.255.255.240
no ip directed-broadcast
delay 10000
tunnel source Loopback0
tunnel destination 190.19.15.185
!
interface Ethernet0
ip address 190.19.15.71 255.255.255.192
no ip directed-broadcast
!
router eigrp 1
network 190.19.0.0
R2#sh ip eig n
IP-EIGRP neighbors for process 1
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
1 190.19.15.135 Tu0 12 00:29:04 864 5000 0 4248
0 190.19.15.74 Et0 13 00:29:11 16 200 0 9125
R2#sh ip rou
190.19.0.0/16 is variably subnetted, 6 subnets, 2 masks
D 190.19.15.160/28 [90/409600] via 190.19.15.74, 00:22:57, Ethernet0
D 190.19.15.176/28 [90/39620096] via 190.19.15.74, 00:22:57,
Ethernet0
C 190.19.15.128/28 is directly connected, Tunnel0
C 190.19.15.144/28 is directly connected, Loopback0
D 190.19.15.0/26 [90/39492096] via 190.19.15.74, 00:22:57, Ethernet0
C 190.19.15.64/26 is directly connected, Ethernet0
R2#sh ip eig to
IP-EIGRP Topology Table for process 1
P 190.19.15.160/28, 1 successors, FD is 793600
via 190.19.15.74 (793600/128256), Ethernet0
P 190.19.15.176/28, 1 successors, FD is 39620096
via 190.19.15.74 (39620096/39594496), Ethernet0
via 190.19.15.135 (2562688000/128256), Tunnel0
P 190.19.15.128/28, 1 successors, FD is 2562560000
via Connected, Tunnel0
P 190.19.15.144/28, 1 successors, FD is 128256
via Connected, Loopback0
P 190.19.15.0/26, 1 successors, FD is 39492096
via 190.19.15.74 (39492096/39466496), Ethernet0
via 190.19.15.135 (2563072000/1152000), Tunnel0
P 190.19.15.64/26, 1 successors, FD is 281600
via Connected, Ethernet0
Steve
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