Qtech QSW-3900-24-SFP-AC [124/245] Configure local preference

Qtech QSW-3900-48-SFP-DC [124/245] Configure local preference
QTECH Software Configuration Manual
9-123
message and BGP connection Holdtime are very important for BGP.
When setting up BGP connection between BGP router and its peer, there must be a negotiation. The
negotiated hold-time should be the smaller one between this BGP router keepalive-interval and peer hold time. If the
negotiated hold-time is 0, keepalive message will not be sent and Holdtime overtime will not be checked.
Configure it in BGP configuration mode.
Configure BGP timer
timers bgp keepalive-interval hold-time
Restore to default timer
no timers bgp
The default value of keepalive-interval and holdtime are 30 and 180 seconds.
Sending interval cannot less than 1 second. If configured Holdtime is not 0, it must be more than 3 seconds.
If keepalive interval is more than 1/3 of the negotiated hold-time, the keepalive interval will be auto-set to be the 1/3
of the negotiated hold-time.
9.2.4 Configure local preference
Configuring different local preference can influence the route choosing of BGP. The larger the local preference value
is, the more chance for coorsponded route to be chosen.
Configure it in BGP configuration mode.
Configure local preference
bgp default local-preference localpref
Restore to default local preference
no bgp default local-preference
The default local preference is 100.
Local preference is sent when IBGP and peer exchanging their Update message.
9.2.5 Configure AS MED
Multi-Exit DiscriminatorMEDis the external metric of route which is different from local preference.
MED exchanges between AS, but the EMD entered AS will not leave it. MED is used for choosing the best route and
the smaller one will be chosen. When a router running BGP which gains the route with the same destination address
and different next hop through different External Peer, it will preferentially make a decision according to MED value
of different route. The route will smaller MED will be chosen the external route of AS with the same condition.
Configure it in BGP configuration mode.
Configure system MED
default-metric metric
Restore to default MED
no default-metric
Default metric value is 0.
The above router only compares the MED from different EBGP peer route in the same AS. Use bgp
always-compare-med command to compare the peer route in the different AS.
Example:
QTECH(config)#default-metric 20
9.2.6 Compare MED from different AS neighbors
MED is used for choosing the best path. The smaller MED value will be chosen. It is recommended to use this
command when the IGP and route choosing method are the same in the corresponded AS.
Configure it in BGP configuration mode.
Compare MED from different AS neighbors
bgp always-compare-med
Stop comparing MED from different AS neighbors
no bgp always-compare-med
Only compare MED from the same AS route path by default.
Make sure different AS use the same IGP and route choosing method before using this command.

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