SGS-6340 Series User Manual

To
area1, Layer 3 switches SwitchA and SwitchB are both in-area switches, area edge
switches SwitchC and SwitchD are responsible for reporting distance cost to all destination
outside the area, while they are also responsible for reporting the position of the AS edge
Layer 3 switches SwitchD and SwitchF, AS exterior link-state advertisement from SwitchD and
SwitchF are flooded throughout the whole autonomous system. When ASE LSA floods in area
1, those LSAs are included in the area 1 database to get the routes to network N11 and N15.
In addition, Layer 3 SwitchC and SwitchD must summary the topology of area 1 to the
backbone area (area 0, all non-0 areas must be connected via area 0, direct connections are
not allowed), and advertise the networks in area 1 (N1-N4) and the costs from SwitchC and
SwitchD to those networks. As the backbone area is required to keep connected, there must
be a virtual link between backbone Layer 3 Switch10 and Switch11. The area edge Layer 3
switches exchange summary information via the backbone Layer 3 switch, each area edge
Layer 3 switch listens to the summary information from the other edge Layer 3 switches.
Virtual link can not only maintain the connectivity of the backbone area, but also strengthen the
backbone area. For example, if the connection between backbone Layer 3 SwitchG and
Switch10 is cut down, the backbone area will become incontinuous. The backbone area can
become more robust by establishing a virtual link between backbone Layer 3 switches SwitchF
and Switch10. In addition, the virtual link between SwitchF and Switch10 provide a short path
from area 3 to Layer 3 Switch F.
Take area 1 as an example. Assume the IP address of Layer 3 SwitchA is 10.1.1.1, IP address
of Layer 3 Switch B interface VLAN2 is 10.1.1.2, IP address of Layer 3 SwitchC interface
VLAN2 is 10.1.1.3, IP address of Layer 3 SwitchD interface VLAN2 is 10.1.1.4. SwitchA is
connecting to network N1 through Ethernet interface VLAN1 (IP address 20.1.1.1); SwitchB is
connecting to network N2 through Ethernet interface VLAN1 (IP address 20.1.2.1); SwitchC is
connecting to network N4 through Ethernet interface VLAN3 (IP address 20.1.3.1). All the
three addresses belong to area 1. SwitchC is connecting to Layer 3 SwitchE through Ethernet
interface VLAN1 (IP address 10.1.5.1); SwitchD is connecting to Layer 3 SwitchD through
Ethernet interface VLAN1 (IP address 10.1.6.1); both two addresses belong to area 1. Simple
authentication is implemented among Layer 3 switches in area1, edge Layer 3 switches of
area 1 authenticate with the area 0 backbone Layer 3 switches by MD5 authentication.
The followings are just configurations for all Layer 3 switches in area 1, configurations for
Layer 3 switches of the other areas are omitted. The following are the configurations of
SwitchA, SwitchB, SwitchC and SwitchD:
1)Switch A:
Configure IP address for interface vlan2
SwitchA#config
SwitchA(config)# interface vlan 2
SwitchA(config-If-Vlan2)# ip address 10.1.1.1 255.255.255.0
SwitchA(config-If-Vlan2)#exit
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