bgp local-as no-prepend replace-as | enable PVST simulation in MSTP on edge ports

[Ibrahim Jamil]

Hello Freinds Which Statement is true about the following command? "bgp local-as no-prepend replace-as" 1. Use in eBGP and iBGP 2. Add the local AS to receive NLRI 3. Remove the orign AS from the advertise NLRI If MSTP Region has a connection to PVST switch,what is the effect of enable PVST simulation in MSTP on edge ports? choose two: . allow the root to be in PVST SW . Send multiple BPDU for each Vlan . Disable the edge port if receive a Superior PVST BPDU Thanks Jamil

[Georg Pauwen]

Hello,

for the first question, it is answer 3:

bgp local-as no-prepend replace-as

This is used for eBGP peers, it removes the local AS, and replaces it with another AS number. The eBGP peer needs to peer with the replaced AS number and not the original AS.

[Giuseppe Larosa]

Hello Ibrahim,

for MSTP PVST emulation allows to have the root bridge either in the MST region or int the PVST region for every PVST instance.

A mix is not allowed.

So the right answers should be:

1) allow the root to be in PVST SW  yes

2) Send multiple BPDU for each Vlan

NO. MST is not able to do this . PVST emulation requires consistent root bridge for all instances either in MST region or in PVST region.

3) Disable the edge port if receive a Superior PVST BPDU 

yes, as part of the consistency check if for a specific Vlan the PVST BPDU is better then the corresponding MST instance BPDU and the root bridge is in the MST region this will cause a PVST emulation inconsistent state and the whole port is placed in this state.

Hope to help

Giuseppe