Ethernet Switching
Ethernet Switching

VCP protcol PDU in Virtual chassis and metric value

‎12-15-2018 04:33 PM

Hi everyone,

1)Virtual chassis protocol factors two things in computing the shortest path from rooted PFE to target PFE.

a) bandwidth 

b) hop count.

From the above link:

When all interfaces have the same bandwidth, as is the case here, the SPF result is effectively based on hop count.


This is what I understand:

SPF first factors in bandwidth in computing the shortest path, if tie, it then considers the hop count to compute the shoretst path from " rooted " PFE to target PFE.

Is my understanding correct?


2)  VCCP uses ISIS protcol .

Cisco implementation uses default metric of 10 for all ISIS enabled links. It does not matter if the link is 10 G or 1 G, this metric is then used to compute the shortest path.

In JUNOS' implementation  , do we have default value too,  regardless of the link bandwidth just like we see in Cisco?


Below I  see metric value of 15 , I am not sure if this the deafult value or if this value was computed using bandwidth as we see in  OSPF?

From the above link:

user@host> show virtual-chassis protocol database member 0 detail

001d.b510.0800.00-00 Sequence: 0x9f5, Checksum: 0x5b2b, Lifetime: 116 secs
   Neighbor: b0c6.9abf.6800.00  Interface: vcp-1/3/0.32768 Metric:      15
b0c6.9abf.6800.00-00 Sequence: 0x9f8, Checksum: 0x326e, Lifetime: 117 secs
   Neighbor: 001d.b510.0800.00  Interface: vcp-5/0/0.32768 Metric:      15


Thanks and have a nice weekend!!










Ethernet Switching
Accepted by topic author sarahr202
‎12-16-2018 07:01 AM

Re: VCP protcol PDU in Virtual chassis and metric value

‎12-16-2018 04:58 AM

I can't find documentation that details this, but it seems to be based on the port bandwidth.  On VC using the build in port I see a metric of 7.


Steve Puluka BSEET - Juniper Ambassador
IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)