H3C Technologies H3C S12500-X Series Switches - Manual (Page 74)

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Cost for packet transmission over the link. Each link has a different cost. The smaller the cost, the
better the link. The route selection algorithm uses this value to determine the best route. The
interface cost is configurable.
FSPF packet types
The following protocol packets are used in FSPF:
• Hello packets—Sent periodically to discover and maintain FSPF neighbors.
• Link state update (LSU)—Advertises local link state information in LSRs to the neighboring switches.
• Link state acknowledgment (LSA)—Acknowledges the received LSR.
After receiving an LSU, a switch needs to acknowledge its LSR with an LSA. Otherwise, the
neighboring switch retransmits the LSR.
How FSPF works
FSPF works as follows:
1. The switch periodically sends hello packets to establish neighbor relationships with other switches.
2. After establishing neighbor relationships, the switches synchronize LSDBs by exchanging all LSRs
in their respective LSDBs. A switch carries LSRs in LSUs and acknowledges received LSRs with
LSAs.
3. After the synchronization is complete, the LSDB in each switch contains LSRs of all switches in the
fabric.
4. The switch uses the Dijkstra algorithm to calculate the shortest paths to other switches based on the
local LSDB. Then, it determines the outgoing interfaces and generates an FSPF routing table.
5. When the network topology or link state changes, the switch floods a new LSR to its neighboring
switches. After receiving the LSR, the neighboring switches add it to their LSDBs and flood it to their
respective neighbors. In this way, all switches in the fabric receive that LSR.
6. Local LSDB updating results in SPF calculation. The calculated shortest path tree list is updated to
the FSPF routing table.
Configuring static routes for FC
Configuration restrictions and guidelines
• The destination address of a static FC route is in the range of 010000 to EFFFFF (hexadecimal). You
cannot configure a route with a well-known address as the destination address.
• The outgoing interface of a static FC route can only be a VFC interface.
• If you configure two routes with the same destination address, mask, and outgoing interface, but
with different costs, the route configured later applies.
• The maximum number of static routes allowed in a VSAN is 256.
Configuration procedure
To configure a static FC route: