03-09-2009 03:28 AM - edited 03-04-2019 03:51 AM
Hi.
Several of my customers pay for redundant connections to our datacenter. At the customer end is an 1812, setup with EIGRP towards our core 6509.
EIGRP works fine as long as the primary link falls down neatly. The problem is those occurences when the primary link either has packet loss or is in a flapping state (the flapping state isn't noticed on the physical layer of any of the devices under my control, as the flapping is happening somewhere in the cloud of the link provider).
Is there any way I can setup the 1812 and the 6509 to notice packet loss/flapping on the primary link and prefer the secondary link as long as the primary link is in such a state?
Kind regards,
Ivar
03-09-2009 06:08 AM
Hello,
What do you have set for your EIGRP weights ie
router eigrp 88
metric weights tos K1 K2 K3 K4 K5
The K4 value measures reliability, this may work for you?
Regards
03-09-2009 06:51 AM
I haven't set "metric weights" in my EIGRP-config.
Does the "metric weights" feature monitor reliability, or is it just static values?
I can't tell the router that the primary link isn't realiable, as it is reliable until it starts flapping/gets packet loss, and I want that to be detected by the router so that the secondary link is preferred until the primary link is fine again.
Which link will be affected by flapping/packet loss I can't know in advance =)
03-09-2009 06:30 AM
Hello Ivar,
check for BFD support: Bidirectional forwarding detection could help
BFD can provide its services to routing protocols
But I don't know if 1812 can support it
see
http://www.cisco.com/en/US/docs/ios/12_4t/ip_route/configuration/guide/t_bfd.html
for example BFD echo detection is supported on
c1805-advipservicesk9-mz.124-24.T.bin
So this is a method you can investigate
Hope to help
Giuseppe
03-10-2009 01:37 AM
Hi. 1812 supports BFD, and I've just setup up two 1812 with redundant links, EIGRP and BFD in my lab, like this:
interface FastEthernet0
ip address 10.10.10.1 255.255.255.252
duplex auto
speed auto
bfd interval 50 min_rx 50 multiplier 3
!
interface FastEthernet1
ip address 10.20.20.1 255.255.255.252
delay 70000
duplex auto
speed auto
bfd interval 50 min_rx 50 multiplier 3
!
router eigrp 1
passive-interface default
no passive-interface FastEthernet0
no passive-interface FastEthernet1
network 10.1.1.0 0.0.0.255
network 10.10.10.0 0.0.0.3
network 10.20.20.0 0.0.0.3
bfd interface FastEthernet0
bfd interface FastEthernet1
auto-summary
!
end
In between the 1812s, on the FA0-link, I've put in a Network Nightmare to make packet loss on the link. With little packet loss (0,5%), neither EIGRP nor BFD notice any problems. With a lot of packet loss (5%), EIGRP goes up and down, and so does BFD...
I expected that BFD would tell EIGRP that the FA0-link isn't reliable while there is packet loss, so EIGRP would prefer FA1...but that doesn't seem to happen.
04-05-2010 01:46 AM
I am also intrested inways of detecting, reporting and woking around problematic links that do not go down completely.
looking at BDF is seems to be just a way of quickly detecting and reporting link failure and not a general quality measurement.
Have you tested the first suggestion of using the EIGRP link quality to change the routing cost ?
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