In this blog article, we’re going to look at the various MVPN
route types and in particular how they look on a Cisco IOS router.
Introduction
My lab is setup using IOS and MVPN profile 13. Please see the references section on how to
configure profile 13.
With profile 13 the C-Multicast signalling is done within
BGP which means we can use standard BGP show commands to troubleshoot our
network. However, at first glance, it
doesn’t necessarily make a lot of sense.
An example output from a PE is below and in this blog post we’ll look at
interpreting all the different route types.
R2#sh bgp ipv4
mvpn vrf red
BGP table
version is 27, local router ID is 33.0.254.2
Network Next Hop Metric LocPrf Weight Path
Route
Distinguisher: 179:2100 (default for vrf red)
*>
[1][179:2100][33.0.254.2]/12
0.0.0.0 32768 ?
*>i [1][179:2100][33.0.254.3]/12
33.0.254.3 0 100
0 ?
*>
[5][179:2100][10.0.24.2][239.0.0.1]/18
0.0.0.0 32768 ?
*>i
[6][179:2100][179][10.0.254.2/32][239.0.0.1/32]/22
33.0.254.3 0 100
0 ?
*>i
[7][179:2100][179][10.0.24.2/32][239.0.0.1/32]/22
33.0.254.3 0 100
0 ?
In the references section, you’ll also find a link to the
IANA assignment for all the route types with a link to the relevant RFC.
Also for reference, here is my lab setup:
Route Type 1 - Intra-AS I-PMSI A-D route
Within my lab, I now strip back all PIM config from my CEs
and run a BGP show command on my PE for the MVPN address family.
At the moment we only have route type 1, which is basically just
used to set up the MPVN tree. As we’re
using BGP to setup the MVPN then it’s classed as A-D (Auto discovery).
R2#sh ip bgp
ipv4 mvpn vrf red
BGP table
version is 27, local router ID is 33.0.254.2
Network Next Hop Metric LocPrf Weight Path
Route
Distinguisher: 179:2100 (default for vrf red)
*>
[1][179:2100][33.0.254.2]/12
0.0.0.0 32768 ?
*>i [1][179:2100][33.0.254.3]/12
33.0.254.3 0 100
0 ?
Let’s break down what each of the fields mean for this route
type:
[1] – This
is the MPVN route type (please see the IANA web link in the references section)
[179:2100] –
This is the RD for the VPN
[33.0.254.2] –
This is the next-hop IP for the BGP peer.
I have two PEs in my topology, so there is a type 1 route for each PE.
Route Type 6 – Shared Tree Join (*,G)
Next, I will add an RP to R2, configure the rest of the network
accordingly and then do an IGMP static join to 239.0.0.1 on one of my CEs.
We now get two new type 6 routes created which is the equivalent
of a (*,G) route to the RP. We’ll ignore
the one to 224.0.1.40 and look at the route related to 239.0.0.1.
R2#sh ip bgp
ipv4 mvpn vrf red
BGP table
version is 29, local router ID is 33.0.254.2
Network Next Hop Metric LocPrf Weight Path
Route
Distinguisher: 179:2100 (default for vrf red)
*>
[1][179:2100][33.0.254.2]/12
0.0.0.0 32768 ?
*>i [1][179:2100][33.0.254.3]/12
33.0.254.3 0 100
0 ?
*>i
[6][179:2100][179][10.0.254.2/32][224.0.1.40/32]/22
33.0.254.3 0 100
0 ?
*>i
[6][179:2100][179][10.0.254.2/32][239.0.0.1/32]/22
33.0.254.3 0 100
0 ?
Let’s break down what each of the fields mean for this route
type:
[6] –
This is the MPVN route type (please see the iana web link in references
section)
[179:2100]
– This is the RD for the VPN
[179] –
This is the BGP AS number I’ve used in this lab
[10.0.254.2/32]
– This is the RP address
[239.0.0.1/32]
– This is the multicast group that we joined
If I now go onto the CE, the equivalent mroute is shown
below for reference:
R5#sh ip
mroute vrf red
(*,
239.0.0.1), 00:04:36/00:02:03, RP 10.0.254.2, flags: SJPCL
Incoming interface: Ethernet0/0.100, RPF nbr
10.0.35.1
Outgoing interface list: Null
Route Type 5 – Source Active
Next, I will ping from one of my CEs to 239.0.0.1 to simulate
a source going active. This will create
a type 5 route.
R2#sh ip bgp
ipv4 mvpn vrf red
BGP table
version is 34, local router ID is 33.0.254.2
Network Next Hop Metric LocPrf Weight Path
Route
Distinguisher: 179:2100 (default for vrf red)
*>
[1][179:2100][33.0.254.2]/12
0.0.0.0 32768 ?
*>i [1][179:2100][33.0.254.3]/12
33.0.254.3 0 100
0 ?
*>
[5][179:2100][10.0.24.2][239.0.0.1]/18
0.0.0.0 32768 ?
*>i [6][179:2100][179][10.0.254.2/32][224.0.1.40/32]/22
33.0.254.3 0 100
0 ?
*>i
[6][179:2100][179][10.0.254.2/32][239.0.0.1/32]/22
33.0.254.3 0 100
0 ?
*>i [7][179:2100][179][10.0.24.2/32][239.0.0.1/32]/22
33.0.254.3 0 100
0 ?
Let’s break down what each of the fields mean for this route
type:
[5] –
This is the MPVN route type (please see the iana web link in references
section)
[179:2100]
– This is the RD for the VPN
[10.0.24.2] –
This is the IP address of the multicast source
[239.0.0.1]
– This is the multicast group that we joined
Route Type 7 – Source Tree Join (S,G)
When we did the ping above you may have also noticed a type
7 route was also created. This is created
as the receiver side CE router switched to the source-based tree. So the type 7 route is an (S,G) route.
Let’s break down what each of the fields mean for this route
type:
[7] –
This is the MPVN route type (please see the IANA web link in references
section)
[179:2100]
– This is the RD for the VPN
[179] –
This is the BGP AS number I’ve used in this lab
[10.0.24.2] –
This is the IP address of the multicast source
[239.0.0.1]
– This is the multicast group that we joined
Also for reference please see the equivalent mroutes:
R5#sh ip
mroute vrf red
(*,
239.0.0.1), 00:14:40/stopped, RP 10.0.254.2, flags: SJPCL
Incoming interface: Ethernet0/0.100, RPF nbr
10.0.35.1
Outgoing interface list: Null
(10.0.24.2,
239.0.0.1), 00:00:05/00:02:54, flags: PLTX
Incoming interface: Ethernet0/0.100, RPF nbr
10.0.35.1
Outgoing interface list: Null
Resources
About the Author
The author of this blog works for Vanguard IT who provide a range of professional services and managed services
For more information go to https://vanguard-it.net
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