sh ip bgp neighbor advertised-routes shows the only routes being advertised to
Y are the routes that should be advertised to them. I checked a variety of
other peers and have the expected results.
>From my perspective:
Packets come in on port A, supposed to leave on port X, but they leave on port
Y. All of the troubleshooting steps I've done on my own (or suggested by
mailing lists) say the packets should be leaving on the desired port X.
>From the customer's perspective, they're supposed to be coming from me on port
>X, but they're arriving on port Y, another network .
Port X in both scenarios is our direct connection, while port Y is a mutual
upstream provider.
Without knowing more about the specific platform, it seems to me like a bug in
the platform. If all indicators (not just configurations, but show commands as
well) say the packet should be leaving on X and it leaves on Y, then I'm not
sure what else it could be, besides a bug.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
Midwest-IX
http://www.midwest-ix.com
----- Original Message -----
From: "David Bass" <davidbass...@gmail.com>
To: "Mike Hammett" <na...@ics-il.net>
Cc: "Matthew Huff" <mh...@ox.com>, "NANOG" <nanog@nanog.org>
Sent: Monday, April 3, 2023 9:12:52 PM
Subject: Re: Cisco Nexus 3k Route Selection\Packet Forwarding Debugging
You said that they are seeing traffic from another upstream…are you advertising
the prefix to them? Are you advertising their prefix to your upstream?
Looks like the route maps are involved in some dual redistribution…might want
to make sure everything is matching correctly, and being advertised like you
want.
On Mon, Apr 3, 2023 at 4:20 PM Mike Hammett < na...@ics-il.net > wrote:
I don't see any route-maps applied to interfaces, so there must not be any PBR
going on. I only see ACLs, setting communities, setting local pref, etc. in the
route maps that are applied to neighbors.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
Midwest-IX
http://www.midwest-ix.com
From: "Mike Hammett" < na...@ics-il.net >
To: "Matthew Huff" < mh...@ox.com >
Cc: "NANOG" < nanog@nanog.org >
Sent: Monday, April 3, 2023 8:26:30 AM
Subject: Re: Cisco Nexus 3k Route Selection\Packet Forwarding Debugging
Only two VRFs, default and manangement. IIRC, everything I saw before mentioned
the default VRF.
I do see a ton of route-maps. It's mostly Greek to me, so I'll have to dig
through this a bit to see what's going on.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
Midwest-IX
http://www.midwest-ix.com
From: "Matthew Huff" < mh...@ox.com >
To: "Mike Hammett" < na...@ics-il.net >
Cc: "NANOG" < nanog@nanog.org >
Sent: Monday, April 3, 2023 8:06:51 AM
Subject: RE: Cisco Nexus 3k Route Selection\Packet Forwarding Debugging
What about VRFs and/or policy based routing?
switch-core1# show vrf
VRF-Name VRF-ID State Reason
default 1 Up --
management 2 Up --
switch-core1# show route-map
route-map rmap_bgp_to_eigrp_b2b, permit, sequence 10
Match clauses:
interface: Ethernet1/33
route-type: internal
Set clauses:
metric 40000000 10 255 1 1500
route-map rmap_bgp_to_eigrp_b2b, permit, sequence 20
Match clauses:
interface: Ethernet1/34
route-type: internal
Set clauses:
metric 40000000 30 255 1 1500
route-map rmap_static_to_eigrp, permit, sequence 10
Match clauses:
ip address prefix-lists: prefix_static_to_eigrp
Set clauses:
route-map rmap_static_to_eigrp_v6, permit, sequence 10
Match clauses:
ipv6 address prefix-lists: prefix_ipv6_static_to_eigrp
Set clauses:
From: Mike Hammett < na...@ics-il.net >
Sent: Monday, April 3, 2023 9:00 AM
To: Matthew Huff < mh...@ox.com >
Cc: NANOG < nanog@nanog.org >
Subject: Re: Cisco Nexus 3k Route Selection\Packet Forwarding Debugging
It could be an sFlow bug, but I come at this from a reported problem and
gathering data on that problem as opposed to looking at data for problems.
The snmp if index reported by the Nexus matches the if index in ElastiFlow.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
Midwest-IX
http://www.midwest-ix.com
________________________________________
From: "Matthew Huff" <mailto: mh...@ox.com >
To: "Mike Hammett" <mailto: na...@ics-il.net >
Cc: "NANOG" <mailto: nanog@nanog.org >
Sent: Monday, April 3, 2023 7:50:08 AM
Subject: RE: Cisco Nexus 3k Route Selection\Packet Forwarding Debugging
SFlow misconfiguration or bug on either the nexus or the sflow monitor? On the
monitor, can you verify that the snmp interfaces are mapped to the correct ones
on the nexus?
From: Mike Hammett <mailto: na...@ics-il.net >
Sent: Monday, April 3, 2023 8:47 AM
To: Matthew Huff <mailto: mh...@ox.com >
Cc: NANOG <mailto: nanog@nanog.org >
Subject: Re: Cisco Nexus 3k Route Selection\Packet Forwarding Debugging
It shows the desired result.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
Midwest-IX
http://www.midwest-ix.com
________________________________________
From: "Matthew Huff" <mailto: mh...@ox.com >
To: "Mike Hammett" <mailto: na...@ics-il.net >, "NANOG" <mailto:
nanog@nanog.org >
Sent: Monday, April 3, 2023 5:38:23 AM
Subject: RE: Cisco Nexus 3k Route Selection\Packet Forwarding Debugging
switch-core1# sh forwarding route x.x.x.x
slot 1
=======
IPv4 routes for table default/base
------------------+-----------------------------------------+----------------------+-----------------+-----------------
Prefix | Next-hop | Interface | Labels | Partial Install
------------------+-----------------------------------------+----------------------+-----------------+-----------------
x.x.x.x/24 x.x.x.250 Ethernet1/29
switch-core1# show routing hash x.x.x.x y.y.y.y
Load-share parameters used for software forwarding:
load-share mode: address source-destination port source-destination
Hash for VRF "default"
Hashing to path *y.y.y.y Eth1/29
For route:
y.y.y.0/24, ubest/mbest: 1/0
*via z.z.z.z, Eth1/29, [90/3072], 1w2d, eigrp-100, internal
From: NANOG <mailto: nanog-bounces+mhuff = ox....@nanog.org > On Behalf Of Mike
Hammett
Sent: Monday, April 3, 2023 1:21 AM
To: NANOG <mailto: nanog@nanog.org >
Subject: Cisco Nexus 3k Route Selection\Packet Forwarding Debugging
We have a Nexus 3064 that is setup with partial BGP tables and is routing based
on that.
I've done a show ip bgp for an IP of interest and it has an expected next hop
IP. I show ip arp on that next hop IP and it has the expected interface.
However, sFlows show the packets leaving on a different interface, the one that
would carry the default route for routes not otherwise known.
If the next hop IP is expected and the ARP of that next hop IP is expected, why
are packets leaving out an unexpected interface?
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
Midwest-IX
http://www.midwest-ix.com
