Bgp Path Selection Configuration - 3Com S7906E Configuration Manual

Network
*>i 9.1.1.0/24
[SwitchD] display bgp routing-table 9.1.1.0
BGP local router ID : 4.4.4.4
Local AS number : 65001
Paths: 1 available, 1 best
BGP routing table entry information of 9.1.1.0/24:
From
Relay Nexthop
Original nexthop: 10.1.3.1
AS-path
Origin
Attribute value : MED 0, localpref 100, pref-val 0, pre 255
State
Not advertised to any peers yet
The output information shows that:
Switch F can send route information to Switch B and Switch C through the confederation by
establishing only an eBGP connection with Switch A.
Switch B and Switch D are in the same confederation, but belong to different sub ASs. They obtain
external route information from Switch A and generate the same BGP route entries; it seems like
that they reside in the same AS although they have no direct connection in between.

BGP Path Selection Configuration

Network requirements
In the figure below, all switches run BGP. Between Switch A and Switch B, and between Switch A
and Switch C are eBGP connections. Between Switch B and Switch D, and between Switch D and
Switch C are iBGP connections.
OSPF is the IGP protocol in AS 200.
Configure routing policies, making Switch D use the route 1.0.0.0/8 from Switch C as the optimal.
Figure 1-26 Network diagram for BGP path selection configuration
AS 100
Vlan-int101
Vlan-int100
Vlan-int200
Switch A
Device
Switch A
Origin : i - IGP, e - EGP, ? - incomplete
NextHop
10.1.3.1
: 10.1.3.1 (1.1.1.1)
: 0.0.0.0
: 100
: igp
: valid, internal, best,
AS 200
Vlan-int100
Switch B
Vlan-int200
Switch C
Interface IP address
Vlan-int101 1.0.0.0/8
Vlan-int100 192.1.1.1/24
MED LocPrf
0 100 0
Vlan-int300
Vlan-int300
Vlan-int400
Switch D
Vlan-int400
Device
Switch D
1-61
PrefVal Path/Ogn
100i
Interface IP address
Vlan-int400 195.1.1.1/24
Vlan-int300 194.1.1.1/24