<div dir="ltr">Hello,<div><br>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.</div>
<div><br></div><div>IE: <a href="http://74.1.1.0/24">74.1.1.0/24</a> announced from a customer over <a href="http://208.123.123.0/30">208.123.123.0/30</a> (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.</div>
<div><br></div><div>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.</div>
<div><br></div><div>Bad path:</div><div><br></div><div><div>SSH@CSR1.LGA1#show ip route 74.1.1.34</div><div>Type Codes - B:BGP D:Connected I:ISIS O:OSPF R:RIP S:Static; Cost - Dist/Metric</div><div>BGP Codes - i:iBGP e:eBGP</div>
<div>ISIS Codes - L1:Level-1 L2:Level-2</div><div>OSPF Codes - i:Inter Area 1:External Type 1 2:External Type 2 s:Sham Link</div><div>STATIC Codes - d:DHCPv6</div><div> Destination Gateway Port Cost Type Uptime src-vrf</div>
<div>1 <a href="http://74.1.1.0/24">74.1.1.0/24</a> 69.123.123.2 ve 47 200/0 Bi 0m7s - </div></div><div><br></div><div>OSPF Neighbor -- the downstream site doesnt even run BGP yet this route is learned via BGP. </div>
<div><br></div><div><br></div><div>Good path:</div><div><br></div><div><div>SSH@CSR1.LGA1#show ip route 74.1.1.34</div><div>Type Codes - B:BGP D:Connected I:ISIS O:OSPF R:RIP S:Static; Cost - Dist/Metric</div><div>BGP Codes - i:iBGP e:eBGP</div>
<div>ISIS Codes - L1:Level-1 L2:Level-2</div><div>OSPF Codes - i:Inter Area 1:External Type 1 2:External Type 2 s:Sham Link</div><div>STATIC Codes - d:DHCPv6</div><div> Destination Gateway Port Cost Type Uptime src-vrf</div>
<div>1 <a href="http://74.1.1.0/24">74.1.1.0/24</a> 208.123.123.2 ve 239 200/0 Bi 2m24s - </div></div><div><br></div><div>The end customer's BGP advertisement.</div><div><br></div><div><br>
</div><div>-James<br clear="all"><div><br></div>-- <br><span style="color:rgb(51,51,51);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><p style="margin:0px"><b><span style="font-size:10pt">James Cornman</span></b></p>
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