Exploring the quirks of Network Engineering
Scenario
The BGP attribute filter can be used, as the name suggests, to filter unsupported or undesired attributes attached to a received prefix. If prefix filtering is enabled for the appropriate attribute, it will be stripped/discarded from the prefix. A list of attributes can be found here. An alternative to discarding the attribute is to use treat-as-withdrawal option – in this instance, the router will treat the prefix advertisement as a withdrawal. This should be used with care as it could break fundamental BGP operations. The below example shows a basic eBGP neighborship implementing filtering/discarding on attribute 30 and treat-as-withdrawal on attribute 31 – both of which are depreciated. The main difference is that XR must uses an attribute-filter.
IOS Config
router bgp 100 |
XR Config
router bgp 100 |