IGRP: AD=100; IP Protocol 9; update 90s, invalidation = 3×90, holddown = invalidation+10, Flush = 7×90
| Metric = {k1*BWIGRP + k2* BWIGRP /256-LOAD+k3*DLYIGRP} * k5/ (Reliability+k4) |
Typically metric = BWIGRP + DLYIGRP; BWIGRP = 10^7/BW in Kbps, DLYIGRP = Delay in 10’s of microseconds. Unreachable DLYIGRP = FFFFFF = 167.8s
router igrp 1
metric weights <tos> k1 k2 k3 k4 k5
EIGRP: AD=90, default 100 hops, max 255 – n/w diameter, not a metric. Hello interval = 5s (on b/c and p-to-p links) 60s otherwise. Holdtime=3xHello. Multicast 224.0.0.10. IP protocol88 Metric = 256*IGRP metric.
Components of EIGRP:
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Protocol dependant modules: IP/IPX/Appletalk. |
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DUAL |
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Neighbor Discovery/Recovery |
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Reliable Transport Protocol |
EIGRP automatically redistributes: IPX -> IPX RIP/NLSP, Appletalk -> RTMP, IP -> IGRP (same AS#)
RTP: Hellos – unreliable m/c, ACK – unreliable unicast, UPDATES – reliable, non-periodic, bound, partial, m/c or u/c. QUERIES – m/c or u/c, reliable, REPLIES – u/c reliable, REQUESTS – unused
m/c flowtimer ……….. expires -> unicast (16 times)
Neighbor Discovery/Recovery: interface:
ip hello-interval eigrp <>
ip hold-time eigrp <>
sh ip eigrp neighbors
DUAL: Uses low-level protocols (RTP+ND/R) to :
- Detect new/loss of neighbors
- Make sure the messages are valid
- Make sure the updates are processed sequentially and correctly
- Establish adjacencies
- Exchange Updates
- Calculate Metrics
R1———————R2———————-R3—
\\\\\\\\\\\\\\\\\\\\\|————————| AD
|————————————————–| FD
Feasibility Condition: AD < FD. If FC is met, the neighbor becomes a Feasible Successor
Topological table contains: Every destination, FS, Successor, FD, neighbor’s AD, i/f.
show ip eigrp topology
Route is PASSIVE <—– INPUT EVENT*
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New FS with lower metric — > add
(or)
New FD < old FD — > update FD
(or)
New Distance — > Send update
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If no FS, route = ACTIVE à initiate Diffusing Computation
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Query Query Query (set reply flag ‘r’)
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If a neighbor has a FS, it sends a reply; else it sends a Query and goes ACTIVE
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SIA if no reply is received from all neighbors within 3 mins
*INPUT EVENTS: Cost change of directly connected link, status change of link, update, query or reply
ACTIVE timer can be changed from 3 mins by: router eigrp 1, timers active-time <>
If no FS is discovered from the replies, the FD is set to infinity so that any non-infinite metric is added as FS.
EIGRP Header:
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Version |
Op Code |
Checksum |
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Flags |
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Sequence # |
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Ack # |
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AS # |
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TLVs |
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Flag=1 => new neighbor, first set of routes.
TLVs: K values, load, reliability, AS#, next-hop, External R.P, metric.
CIDR: address aggregation by IANA
EIGRP performs unequal load balancing using VARIANCE: router eigrp 15; var 5
Maximum paths: 1->16, default 4.
*!* Implicit default command: traffic-shape balanced. If only the least cost path needs to be used, but all other routes need to be injected into the routing table, use traffic-shape min
Multiple EIGRP instances: to prevent inter-instance updates, define the i/f in AS1 as a passive i/f for the other AS etc. or use very specific wildcard bits so the exact n/w is matched. router eigrp 10; network 172.20.15.0 0.0.0.255
router eigrp 10; no auto-summary – stops auto-summarization at the n/w boundary
Stub: updates contain only directly connected, static, summary or redistributed networks. router eigrp 10; eigrp stub {connected|static|direct|summary|receive-only}
show eigrp neighbor detail – indicates ‘stub’
To summarize: interface: ip summary-address eigrp 10 172.0.0.0 255.0.0.0
Authentication: same as RIPv2 key-chain; Supports only MD5
i/f: ip authentication key-chain eigrp 10 KC.
Troubleshooting: debug eigrp packets, debug eigrp neighbor
SIA: IOS 12.2[4.1] onwards have a SIA retransmit timer. Enables a route to be active for upto 6 mins before going SIA
|——————————||——————————||——————————————–|
0 90 180 360
Q0,R0 Q1,R1 Q3,R3 SIA
As long as a neighbor responds to a query, the SIA re-tx and Active timers are reset (3 attempts)
SIA causes: low b/w, congestion, resource issues (CPU/memory). EIGRP uses a max of 50% of the b/w by default. Interface: ip bandwidth-percent eigrp 200 (eg 56k link)
