[f-nsp] MLX Route issues after 5.4.0d upgrade

[James Cornman]

Hello,

I've come across some strange routing on an MLX8 (NI-MLX-MR) where the next
hop for a route that is learned via BGP is overwritten by an OSPF neighbor.
The routes are cycling every 10 seconds or so as well.

IE: 74.1.1.0/24 announced from a customer over 208.123.123.0/30 (customer
is .2 and we're .1). Arbitrarily, the next hop will be overwritten with a
next-hop IP of another downstream router in the network, say, 69.123.123.2.
That OSPF neighbor is an NSSA in a area 4. The odd thing is that the
redundant pair for this device was upgraded 60 days ago and hasn't shown
these symptoms so it seems very safe to upgrade. Its as if that neighbor's
advertisement for the next hop, learned by way of its redundant connection
to a different device, is being seen as better than the directly connected
neighbor. Upping the OSPF cost to that downstream site seems to band-aid
the issue but it seems that this should not be occurring at all.

This only started occurring after upgrading from 5.3f to 5.4d. No other
topology changes were introduced at the same time. I'm curious if anyone
else has seen strange behavior like this. Totally seems like a bug of some
sort for which I'll try to convey to Brocade.

Bad path:

SSH at CSR1.LGA1#show ip route 74.1.1.34
Type Codes - B:BGP D:Connected I:ISIS O:OSPF R:RIP S:Static; Cost -
Dist/Metric
BGP  Codes - i:iBGP e:eBGP
ISIS Codes - L1:Level-1 L2:Level-2
OSPF Codes - i:Inter Area 1:External Type 1 2:External Type 2 s:Sham Link
STATIC Codes - d:DHCPv6
        Destination        Gateway         Port          Cost          Type
Uptime src-vrf
1       74.1.1.0/24    69.123.123.2   ve 47         200/0         Bi   0m7s
  -

OSPF Neighbor -- the downstream site doesnt even run BGP yet this route is
learned via BGP.


Good path:

SSH at CSR1.LGA1#show ip route 74.1.1.34
Type Codes - B:BGP D:Connected I:ISIS O:OSPF R:RIP S:Static; Cost -
Dist/Metric
BGP  Codes - i:iBGP e:eBGP
ISIS Codes - L1:Level-1 L2:Level-2
OSPF Codes - i:Inter Area 1:External Type 1 2:External Type 2 s:Sham Link
STATIC Codes - d:DHCPv6
        Destination        Gateway         Port          Cost          Type
Uptime src-vrf
1       74.1.1.0/24    208.123.123.2  ve 239        200/0         Bi
2m24s   -

The end customer's BGP advertisement.


-James

-- 

*James Cornman*

jcornman at atlanticmetro.net
212.792.9950
*
Atlantic Metro Communications, Inc.*

*4 Century Drive, Parsippany NJ  07054*

*
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