Owner's Manual

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- Multihop —Configure an EBGP multihop session. External confederation peering is a special
case that allows unconnected third-party next hops. You do not need to configure multihop
sessions explicitly in this particular case; multihop behavior is implied.
If you have confederation external BGP peer-to-loopback addresses, you still need the
multihop configuration.
If you omit this statement, all EBGP peers are assumed to be directly connected (that is, you
are establishing a nonmultihop, or “regular”, BGP session), and the default time-to-live
(TTL) value is 1.
-
Multihop TTL —Configure the maximum TTL value for the TTL in the IP header of BGP
packets. Range: 1 through 255 Default: 64 (for multihop EBGP sessions, confederations,
and internal BGP sessions)
-
Multihop - No next hop change —Specify not to change the TTL value; for next-hop-to-self
route advertisements, specify the no-nexthop-self option.
-
Authentication Key —Configure an MD5 authentication key (password). Neighboring routers
use the same password to verify the authenticity of BGP packets sent from this system. It can
be up to 126 characters.
-
Hold Time —Value to use when negotiating a connection with the peer. The hold-time value is
advertised in open packets and indicates to the peer the length of time that it should consider
the sender valid. If the peer does not receive a keepalive, update, or notification message
within the specified hold time, the application closes the BGP connection to the peer and
routers through that peer become unavailable.
The hold time is three times the interval at which keepalive messages are sent. Range: 6
through 65,535 seconds Default: 90 seconds
-
Metric Out —Metric for all routes sent using the multiple exit discriminator (MED, or
MULTI_EXIT_DISC) path attribute in update messages. This path attribute discriminates
among multiple exit points to a neighboring AS. If all other factors are equal, the exit point
with the lowest metric is preferred.
You can specify a constant metric value by selecting the first radio button option. For
configurations in which a BGP peer sends third-party next hops that require the local system
to perform next-hop resolution-IBGP configurations, configurations within confederation
peers, or EBGP configurations that include the multihop command-you can specify a variable
metric by selecting the second or third radio buttons for the IGP or Min IGP option.
You can increase or decrease the variable metric calculated from the IGP metric (either from
the igp or igp-minimum statement) by specifying a value for
<offset> . You can specify this
offset by entering a value into the text fields next to the
IGP or Min IGP options. The metric
increases when you specify a positive value for
<offset> , and decreases when you specify a
negative value for
<offset> .
igp—Set the metric to the most recent metric value calculated in the IGP to get to the
BGP next hop.