This is not necessarily true. CDP & VTP both use vlan 1, if the native vlan is 1 they will be untagged, if the native vlan is anything other than 1 they will all be tagged with 1 and both will work regardless of whether or not vlan 1 is allowed on the trunk. DTP & BPDUs are never tagged but do not necessarily have any association with a vlan. This is typically how traffic that is intended to be switch to switch is treated, such as PAgP and LACP.
I have seen trouble with switch technologies working in the past when I disallowed the native vlan, but that was a bug which Cisco logged and fixed with 1000v. Otherwise, either tagging or disallowing the native vlan should be fine. Some switches do not support the tag native vlan option, so there may be no other choice besides disallowing it.
the native vlan is by default vlan 1. The recommendation is to create a new vlan eg. vlan 999 is what we used, do not create a L3 SVI for it because the native vlan never needs to be routed, do not allocate any port into because no device ever needs to be in the native vlan and do not allow it on any trunk links.
Question We run asr9001 with XR 6.1.3, and we have a very long delay to
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