EIGRP

Multicast updates on 224.0.0.10
Criteria for adjacency forming:
Same AS number
Source IP of Hello from same subnet as Primary IP add on interface on which Hello is recvd
K values must match
Authentication must pass

Hello & Dead Intervals need not match.

Updates:
Full updates when neighbor comes up for first time.
Full updates on neighbor recovery from failure
Partial updates when routes change
Update queries are multicast, waiting for ack. If no ack recvd within RTO then query is unicast to specific neighbor. Ack are unicast. Update & ack contain sequence No.

EIGRP Tables:
· Neighbor table-maintain adjacencies
· Topology table-contains entire topology to each network. Feasible successors are stored here.
· Routing table-best paths are chosen from topology table & populated here.

Composite Metrics:
Bandwidth, load, delay, reliability, MTU
K values can be changed with “metric weights tos k1 k2 k3 k4 k5”
BW = 10pwr7/kbps on interface
Delay = is in units of 10msec. delay of 1 = 10msec
Metric = 256 * BW + 256 * delay

If a route for a destination fails, then:
IF FS routes exist, then install lowest metric FS in to routing table.
If no FS exist, query neighbors for updates

Feasibility condition: to be a FS, reported distance of the route from a neighbor must be less than existing routers feasible distance.

SIA (stuck in active): if a router doesn’t recv a reply from a neighbor for a query within a specific time i.e. active timer, then router puts that route in to Active state.

Stub router: shouldn’t be a transit router. Stub rtr doesn’t recv query messages.

Variance- multiplier used for load-balancing across unequal cost paths.
Traffic-share balanced: more pkts sent to low metric routes.
Traffic-share min: sends traffic only on lowest metric route.
Traffic-share balanced across-interfaces: rtr choose routes with diff outgoing interfaces.