T-Series Traffic Director Installation, Configuration and Administration Guide
4-3
OSPF Configuration
•
VLAN 406 with /24 subnet. Used for Egress traffic from each T1000 to internet side
switches.
•
VLAN 306 and 506 with /24 subnet.. Used for traffic between internet switches and
content servers.
•
VLANs for management and remote Internet access, and between T1000 and OSN
blades are not shown.
OSPF Functions
Using OSPF in a network, the following steps of operation will take place:
•
OSPF routers send HELLO packets out all interfaces participating in the OSPF
process. If the router and the router on the other side of the connection agree on the
parameters set forth in the HELLO packet, the routers will form neighbor
relationships.
•
Some of the neighbors will form adjacencies. Forming adjacencies is dependent
upon the type of network the HELLO packet is being sent across and the types of
routers exchanging the HELLO packets.
•
The routers will send
link-state advertisements
(LSAs), which contain descriptions
of the router's links and the state of each link to the adjacent router.
•
The routers that receive the LSAs will then record the information into their
link-state database and forward the LSAs on to their respective neighbors. This
allows all routers participating in the OSPF process to have the same view of the
network, although from their own perspective.
•
After learning all LSAs, each router will run the Dijkstra SPF algorithm to learn the
shortest path to all the known destinations. Each router uses this information to
create its SPF tree. Then its routing table is populated with the lowest metric routes.
Given the OSPF operation, packet flows are as follows:
1.
User performs a request towards Internet and packet is destined to the wireless-side
router.
2.
Wireless router checks its routing table to determine the routing path, through
wireless switch 1 or switch 2, that packet should be forwarded to reach the
destination IP address with the lower cost.
3.
Each node on this path will forward the packet to the next hop based on its routing
table populated by OSPF process.
4.
Finally, Internet-side router receives the packet from one of the Internet switches and
forwards it to the destination server.
5.
Replies from Internet back to the user will be routed through nodes that propagate
client subnet with the lower cost following the same rationale.
6.
If any of OSPF nodes fails, then the next available low cost path, advertising the
same subnet, will be elected to forward traffic.
Summary of Contents for ByteMobile T1010
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