From: Brown, Patrick (NSOC-OCF} (PBrown4@chartercom.com)
Date: Thu Aug 14 2003 - 19:58:51 GMT-3
Increasing the mtu to 1504 is recommended when doing dot1q tagging to allow
for the overhead. 802.1Q tunneling feature increases the frame size by 4
bytes when the tag is added. You can increase it globally by "system mtu
1504", or just on that vlan. The bpdufilter will not error-disable the port,
but instead just disable portfast if enabled on the port. Mabey it's just
for protection!
HTH
Patrick B
-----Original Message-----
From: Jason Cash
To: ccielab@groupstudy.com
Sent: 8/14/2003 5:36 PM
Subject: 3550- BPDU filter
Looking over an IPE Appendix J, task 9 reads:
Your customer would like to have their VLANs remain consistent across
your
network. You do not want other customers of yours to learn of their
VLANs
from your network. You want to assign the VLANid of 22 to all frame
that
will be "double-tagged"
The solution is provided as
vlan dot1q tag native
!
vlan 22
mtu 1504
!
interface FastEthernet0/2
switchport access vlan 22
switchport mode dot1q-tunnel
no ip address
l2protocol-tunnel shutdown-threshold stp 1024
l2protocol-tunnel shutdown-threshold vtp 1024
l2protocol-tunnel stp
l2protocol-tunnel vtp
no cdp enable
spanning-tree bpdufilter enable
I am curious as to why vlan 22 was set with an MTU of 1504.
Why was bpdufilter enabled? Does this prevent Vlan22 from being learned
on
the network?
This archive was generated by hypermail 2.1.4 : Tue Sep 02 2003 - 18:53:59 GMT-3