Requiring the first as to be the neighbor’s as – Brocade BigIron RX Series Configuration Guide User Manual
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BigIron RX Series Configuration Guide
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Requiring the first AS to be the neighbor’s AS
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Here are the default administrative distances on the BigIron RX:
•
Directly connected – 0 (this value is not configurable)
•
Static – 1 is the default and applies to all static routes, including default routes. This can be
assigned a different value.
•
EBGP – 20
•
OSPF – 110
•
ISIS – 115
•
RIP – 120
•
IBGP – 200
•
Local BGP – 200
•
Unknown – 255 (the router will not use this route)
Lower administrative distances are preferred over higher distances. For example, if the router
receives routes for the same network from OSPF and from RIP, the router will prefer the OSPF route
by default. The administrative distances are configured in different places in the software. The
device re-advertises a learned best BGP4 route to neighbors by default, regardless of whether the
route’s administrative distance is lower than other routes from different route sources to the same
destination.
•
To change the EBGP, IBGP, and Local BGP default administrative distances, see the
instructions in this section.
•
To change the default administrative distance for OSPF, RIP, ISIS, refer to
•
To change the administrative distance for static routes, refer to
To change the default administrative distances for EBGP, IBGP, and Local BGP, enter a command
such as the following.
BigIron RX(config-bgp)# distance 200 200 200
Syntax: distance <external-distance> <internal-distance> <local-distance>
The <external-distance> sets the EBGP distance and can be a value from 1 – 255.
The <internal-distance> sets the IBGP distance and can be a value from 1 – 255.
The <local-distance> sets the Local BGP distance and can be a value from 1 – 255.
Requiring the first AS to be the neighbor’s AS
By default, the BigIron RX does not require the first AS listed in the AS_SEQUENCE field of an AS
path Update from an EBGP neighbor to be the AS that the neighbor who sent the Update is in. You
can enable the device for this requirement.
When you enable the device to require the AS that an EBGP neighbor is in to be the same as the
first AS in the AS_SEQUENCE field of an Update from the neighbor, the device accepts the Update
only if the ASs match. If the ASs do not match, the device sends a Notification message to the
neighbor and closes the session. The requirement applies to all Updates received from EBGP
neighbors.
To enable this feature, enter the following command at the BGP configuration level of the CLI.