Home > Uncategorized > Multicast on the 7750 – Quick Intro

Multicast on the 7750 – Quick Intro

I’ve been feeling somewhat lethargic since passing my CCIE.  I think it’s actually some sort of trauma, going from 100 in a 50 zone to a dead stop and just lying on the pavement in the rain.  I am really struggling with motivation to do anything really outside of work so it’s time to throw off the shackles of post-CCIE depression and get back to doing something interesting. I’m going to be doing some stuff with multicast on the 7750s so this is the first post on it. I haven’t had time to actually do anything of much substance in the lab on it yet so I just knocked up a quick bit of PIM to highlight how easy it is to get basics up and running. It’s not very interesting but it’s a start. I plan to get in to Rosen and mLDP stuff in the future and do a post on inter AS VPN between SROS and XR, maybe Junos if it treats me nice.

First the topology: R3 and R4 will be PIM neighbours with R4 being our RP.

pim_rp

OK let’s get PIM working:

R4
config router pim
interface system
exit
interface to_R3_1/1/2
exit

R3
config router pim
interface system
exit
interface to_R4_1/1/2
exit

Don’t forget your CPM filters will need to allow PIM through. The above was done on an SR1 which doesn’t support them but they would look something like this:

configure system security cpm-filter ip-filter entry 100
match protocol "pim"
action accept

!!Don’t forget how dangerous misconfiguring filters can be or you will be in the car with your console cable to recover the device!!

Right that should be it for PIM, let’s see if we have neighbour lift off.

*A:R3# show router pim neighbor


===============================================================================
PIM Neighbor ipv4
===============================================================================
Interface Nbr DR Prty Up Time Expiry Time Hold Time
Nbr Address
-------------------------------------------------------------------------------
R4_1/1/2 1 1d 18:47:24 0d 00:01:21 105
34.34.34.4
-------------------------------------------------------------------------------
Neighbors : 1

Great stuff, now we will configure R4 as the RP (bsr and rp candidate) and make sure R3 figures this out. We will use the system address of R4

R4
config router pim
rp
bsr-candidate
address 44.44.44.44
no shutdown
exit
rp-candidate
address 44.44.44.44
no shutdown
exit
exit

And the proof/pudding relationship:

*A:R3# show router pim status | match post-lines 13 BSR
BSR State : Accept Preferred


Elected BSR
Address : 44.44.44.44
Expiry Time : 0d 00:01:19
Priority : 0
Hash Mask Length : 30
Up Time : 1d 18:39:01
RPF Intf towards E-BSR : R4_1/1/2
.
Candidate BSR
Admin State : Down
Oper State : Down
Address : None
Priority : 0
Hash Mask Length : 30
.
Candidate RP
Admin State : Down
Oper State : Down
Address : 0.0.0.0
Priority : 192
Holdtime : 150

So we can see R3 has in fact learned R4 is the BSR. Just to illustrate the point that R3 is not in the running for RP, we can see that both RP and BSR candidate are admin down by default.

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