EIGRP– Enhanced IGRP
Show ip route - connected route
EIGRP– Enhanced IGRP – cisco property – No multi-vendor support only works on cisco router.
Routing table updates whenever changes occurred that time it will update.
1. Fast Convergence
2. Feasibility summarization (Auto Summarization or manual summarization at any interface or specific interface. Default auto summarization enabled. To disable use command:
# No auto-summary
# interface s0/0
#ip summary-address Eigrp 7 192.168.1.0 255.255.252.0 (subnet mask, AD administrative Distance).
#ip summary-address eigrp 7 0.0.0.0 0.0.0.0
3. Backup router.
4. Unequal load balancing (Variance command)
Setup unequal cost load balancing assign a variance of 2 under eigrp process which multiple of the best matric value. After that now uses all loop free path which is less than the multiple of best matric value.
#router eigrp 7
# Variance 2
support default - 4 rotuers, 6is max. new rouers Max 16
# Maximum-pat No
no - 1,2,3,4...
#show ip protocol
support default - 4 rotuers, 6is max. new rouers Max 16
# Maximum-pat No
no - 1,2,3,4...
#show ip protocol
5. Combination of distance and link state (Distance –forms the neighbors information,
Link state – first time send updates information. After that when changes occurred in the routing table then only update.
6. Support VLSM, Classless
7. Dual algorithm (defusing update algorithm to find the best path with loop free).
8. Authentication between two routers. Its use only MD5. (Preconfigured, shared password) each of the (routing update packets also) packets verify if matches then only allow.
key chain, MD5, Key number (multiple number),
# IP authentication mode eigrp ASN MD5
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).
key chain, MD5, Key number (multiple number),
# IP authentication mode eigrp ASN MD5
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).
9. IGRP is ran in same ASN as EIGRP , both automatically redistribute the routes.
EIGRP – Hybrid LS and DV
(RTP used to update the msg - Full update or partial update.)
Metric : Bandwidth, Delay, Load & Reliability
Metric = 256*(K1*bandwidth+ k2*bandwidth/256-Load+k3*delay)*k5/reliablility+k4
2 option: router need to check for the fessible successor. if no fessioble successor. the sucessor router need to run DUAL algorithm again to find a new loop free router to the destionation & add it to the routing table.
EIGRP – Hybrid LS and DV
Cisco property Support multiple protocolonly run in Cisco routers
EIGRP – Hybrid LS and DV (Send first time send full updates) LS(Changes in the topology table )
AS no for admin convenience
Metric = bandwidth delay load , reliability & mtu
Lowest metric is called successor
EIGRP General
(RTP used to update the msg - Full update or partial update.)
Recognize other neighbors
Hello packets (MSG)
224.0.0.10- Must match: Same ASN, Same K Value, Same Authentication, Same Subnet then only its forms neighbor relations.
Metric : Bandwidth, Delay, Load & Reliability
Metric = 256*(K1*bandwidth+ k2*bandwidth/256-Load+k3*delay)*k5/reliablility+k4
Support VLSM
Recognize the down state of neighbors
Hold time: 15 secs LAN, 60 Frame relay, 180 WAN
Per interface basics.
EIGRP ASN timer and hold timer can change. (Note: only change the hold timer don’t change hello timer) timer must be 1:3 (1hello: 3 Hold)
Sucessor router fails2 option: router need to check for the fessible successor. if no fessioble successor. the sucessor router need to run DUAL algorithm again to find a new loop free router to the destionation & add it to the routing table.
Auto summarization at any point.
Manual summarization at any router.
multiple routed protocol support.
multiple routed protocol support.
Unequal load balancing
Fast convergence
Link goes down eigrp processed by next best path
DUAL Algorithm
Simple configuration, more features. Using Multi cast addressing 224.0.0.10. Administrative distance 90.
Same network but different path
EIGRP keep both primary and backup information stored in the topology table.
First best path : stored in the routing table. Primary information is called successor.
Routers which have lowest metric is called successor.
Metric calculation base on the bandwidth (K1-1), delay (K3-1), reliability (K4-K5 -0) and load (K2-0).
Second best path: stored in the topology table. Feasible successor.
If routers have multiple paths enabled router meets FC. Backup router called feasible successor. Successor fails, FS feasible successor takes over.
If condition (FC) fail. There no feasible successor.
so the sucessor router need to run once again DUAL algorithm to find a new loop free router to the destionation & add it to the routing table.
Eigrp Tables
EIGRP Maintaining 3 tables:
Routing Table:. Successor information store. Routing table contain the best route information.
Neighbors table: Neighbor table built from Eigrp hellos and used for reliable delivery.
Topology Table: contain Eigrp routing information for best path (successor) /and loop free alternative path (feasible successor) in this table
Status
Active:Bad - Router become invalid into action to get FS (Feasible successor).
Looking for backup. Query sends to find the backup.
Passive:Good – Everything working normal.
EIGRP Packets
5 types of packets:
Hello packets: Hello packets send every 5 secs to discover neighbor router to keep alive (using multicasting address 224.0.0.10) to form neighbor relation.
Hold timer 15secs in T1 or point to point line. If less than t1 line hello packet send every 60secs and hold time 180 secs.
Note: EIGRP first starts its uses hello packets to build neighbor table. Neighbors are directly attached router that has to match AS (autonomous system) and K value.
Updates:send the routing table with updates. (if any changes in the topology table update).
Query:requesting specific route information.
Reply:respond to Query.
Ack: the update query and reply msg acknowledgement.
EIGRP Configuration
#router EIGRP 7 (7 autonomous system no)
#network 17.16.0.0 (network)
Or only specific range or only one ip
#network 172.16.0.0 0.0.0.255 (network id and wcm)
Default route:
# ip default route 0.0.0.0
#ip route 0.0.0.0 0.0.0.0 10.1.1.2 (Next hop)
#router eigrp 7
#network 0.0.0.0
#passive-interface interface f0/0
Turnoff all the protocol all interface:
#passive- interface default
Trouble Shooting Commands
Show ip router – routing table
Show ip route - connected route
Show ip Eigrp router – only route learnt from Eigrp
Show ip protocols – verifies autonomous system, timer value, identify networks, EIGRP neighbors (routing information successor)
Show ip eigrp topology: identify successor and feasible successor
Show ip eigrp neighbors: neighbors table.
Show ip eigrp traffic - amount & type of eigrp msg.
Show ip eigrp interface e0
Show ip eigrp traffic - statics regarding EIGRP MSG send/receive.
show ip eigerp accounting - display eigrp RID/ ASN
show ip eigerp accounting - display eigrp RID/ ASN
EIGRP Tables
Route table: /Best route : successor lowest metric
Topology table: best route but less desirable but still valid
(FS Backup route)
FS = Reporting Distance (Advertise D) < Feasible D of Successor – For Loop Preventing
Neighbors Table.
EIGRP- Enhanced Interior Gateway Routing Protocol - Interview Questions
1. What is EIGRP?
EIGRP (Enhanced interior Gateway Routing Protocol) is dynamic routing protocol helps the routers to exchange the routing information’s. This is Hybrid protocol. Cisco proprietary protocol. Only works in cisco routers. Hybrid means – (Link stage and Distance vector process) – First time only send full updates to other router after that changes in topology table that time only it will update to other routers.Matric – Bandwidth, delay, reliability, load, MTU…
Lowest Matric is called Successor
Administrative Distance 90.
2. What are the tables in EIGRP?
Three tables in EIGRP:
(1). Route table:routing table contains the routing information (best route) – lowest matric value called successor. [ first bast path store in route table. primary information called successor.
(2). Topology Table: best route but less desirable but still valid – Feasible successor (Backup Router). Loop free alternate path called feasible successor.
keep both primary and backup information stored in topology table.
Feasible successor (backup router information).
FS= Reporting Distance (Advertise distance)< Feasible Distance of Successor
FS For Loop preventing
(3). Neighbors table: Contains the neighbor’s information. (Discover, learn the address and store information).
3. What are the packets in EIGRP?
Hello, Update, Query, Reply and Acknowledge.
Hello : Hello packets send every 5 seconds for keep alive with the help of multicast address 224.0.0.10
Update : if any changes in the topology table it will update. (sending the routing table with updates)Query : For request (requesting specify route information)
Reply : Reply for the Query
Acknowledge : finally acknowledge
4. What is active and passive in EIGRP?
Active: Active means bad router. It’s not a valid router. Query send to find the backup router.To get Feasible Successor (looking for backup router).
Passive: Good. Working fine without any problem.
5. Tell me EIGRP advantages?
6. How to configure summarization on specific interface in EIGRP?Auto Summarization or manual summarization at any interface or
specific interface.
Default auto summarization enabled. To disable use command:
# No auto-summary
# interface s0/0
#ip summary-address Eigrp 7 192.168.1.0 255.255.252.0 (subnet mask, AD administrative
Distance).
#ip summary-address eigrp 7 0.0.0.0 0.0.0.0
7. What is use fo varience Command in EIGRP?Variance command used for setup unequal cost load balancing assigning variance 2.
#router eigrp 7
# Variance 2
8. What are the types of authentication will support EIGRP?
MD 5 Authentication between two routers while routing updates).
key chain, MD5, Key number (multiple number),
# IP authentication mode eigrp ASN MD5
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).
OSPF– Link State Protocol
Hello Packets send every 10sec – to make neighbors table
Metric – 10power 8 /bandwidth
LSA Made, State link broadcast – finally each routers knows entire Topology
Dijiktra’s Algorithmrunning to find best path
Every 30 sec sending LSA Broadcast
Links goes down OSPF algorithm need to run.
Area for administrative convenience
Works all the routers
Support onlyip protocol
LSA flooding: DR /BDR /OBDR
DR: based on the priority and router id. If priority is same and check
Router id (highest ip add)
DR:224.0.0.6
BDR:224.0.0.5
Router(Config)# router ospf process id
Network NID WCM area area no.
(process id should not same but area no should be same)
Show ip ospf interface e0
Sh ip ospf neighbors
OSPF Types of network
Broadcast multi-access
Single packet delivery to all nodes on the network DR and BDR required
NBMA Allow multi-access but no broadcast ability special ospf config
Point to Point –direct connection no dr and bdr required
Point to multipoint
Single interface on one router and multiple destination router.
OSPF General
Backbone router: Area 0
All routers should connect to this area.
Area Border router:
Connected to other routers but atleast one interface connected to area 0
Autonomous System Border Router
Places router from another protocol into OSPF domain router distribution
Summarization can done only ABR or ASBR
Regular area: Non backbone area its database contains both internal and
External routes
Stub Area: Database contain only internal routes and a default route
totally stubby area: database contains routes only for its own area & default
Non so stubby area:
database contain internal routes, routes distributed from connected routing
Process and optionally a default route
LSA7 advertises routes in another routing domain Generated by an ASBR with in a NSSA
Link state routing protocol OSPF & IS-IS
OSPF router identified by RID (router ID) in the entry of Link State Database (LSDB).
Router id – router picks the highest IP address out of all up interfaces.
Router id is chosen when the IOS is initially loaded. New address won’t take after restated by Clear ip OSPF process then reload the router.
Neighbor forms:
Same subnet then discover the OSPF neighbors, OSFP send hello packets out 224.0.0.5
LSA send out 224.0.0.6
Condition:
Same subnet mask and same sub net
Hello time 10 secs by default and dead time = 4*hello time
OSPF area id <=50
Authentication password
When discover other neighbors, the routers run spf algorithm to fill their routing table. In the beginning, both a and b are down. If router a receives router b’s hellow message (with router A not on the list of neighbors) and decide that router b can be a neighbor (all criteria meet) . This is initialization. This is two way state for neighbors.
Both ther tourers recognize others, they began exchange their LSDB.
Point to point topology 2 routers directly connected to each other. In case LSDB are directly advertised and updated between the routers until they both become fully adjacent.
If 10 routers on the same subnet, you would be over load of the traffic. In this case you need Designated Router (DR) that act as the boss that distribute the information to all the employees.
Employees are not allowed to talk to each other. DR has a backup called BDR. All other routers are known as DROTHER.
DR election. Range 0-255 with o never considered for election.
Highest OSPF Priority becomes DR, if Priority ties, Highest RID wins.
Second highest OSPF become BDR, if priority ties second highest RID wins.
Show ip ospf database - LSA contain an entry for each know routers RID, Its interface, ip address mask and subnet. As well as all the routers reachable from that router.
Logical division called AREA.
Area border routers between areas and facilitated communication between routers by manual summarize the routes (this reduce the number of routes).
Belongs to both areas and require more memory and cpu since its process router about both areas.
Configuration:
# router OSPF <Porcess Id> process id 1-65535
optional
# router-id id-value
Configure ip address for loop back interface.
# network ip address wildcard mask area area-id
# network 10.2.1.0 0.0.0.255 area area 2
optional
# IP ospf hello-interval time
# ip ospf dead-interval time
# ip ospf retransmit-intervel time
Interface authenticaton
# ip ospf authenticaton
Router command
# area authentication
Optional
Multiple equal cost routes using the Maximum-path number router subcommand.
Show ip ospf interface
Loadbalance over 4 equl-cost paths. It can support 16 routest by configuration.
Hello send broadcast link every 10 secs non broadcast 30secs
Router with N neighbors have N SPF tree
Interface Area
ClearText (interface)
(config-if)#ip ospf authentication
(config-if)#ip ospf authentication-key PASS
ClearText (AREA)
(config-router)#area A_ID authentication
(config-if)#ip ospf authentication-key PASS
MD5 (interface)
(config-if)#ip ospf authentication messagedigest
(config-if)#ip ospf message-digest-key KEY_NO md5 PASS
MD5 (Area)
(config-router)#area A_ID authentication message-digest
(config-if)#ip ospf message-digest-key KEY_NO md5 PASS
Password MUST be less than 16 characters. Key number doesn’t have to match, If both are configured.
interface commands take precedence.
Types of key generated can be detect
#Debug ip ospf adj (everything)
#Show ip ospf interface
#show ip ospf neighbor
router#show ip ospf 1 neighbor
Router#show ip ospf 1 neighbor detail
rouRouter#show ip route
Router#show ip route ospf
Router#show ip route ospf 1ter#show ip OSPf 1 database
LSA Types:
LSA Type: 1 (Router LSA)
Each router creates its own LSA to represent itself for each area it connects to.
Lists the RID and all interfaces IP addresses on that router that are in that area.
Represents stub networks as well.
LSA Type: 2 (Network LSA)
One per network. Created by the DR on the subnet, and represents the subnet and the router
interfaces connected to the subnet.
LSA Type 3 (Net Summary)
Created by ABRs to represent subnets listed in one area’s type 1 and type 2.
LSA advertised into another area. Defines the links (subnets) in the origin a area, and cost, but no topology data.
LSA Type 4 ASBR summery advertises route to reach ASBR
Generated and advertised by ABR
LSA Type 5 AS external advertise External routes
Generated and advertised by ASBR
LSA Type 6 Group Membership defined for MOSPF: Not supported by CISCO IOS
LSA Type 7 NSSA External created by ASBRs inside an NSSA area, instead fo a type 5 LSA.
LSA Type 8 External Attributes – not implemented in cisco routers.
LSA type 9 to 11 LSA for future Extension of OSPF. Example type 10 LSA for MPLS traffic.
OSPF Packets: (Database Exchange)
Hello packets. – used to discover neighbors and match the criteria then it will become neighbors. To bring a neighbor relationship to a 2way state, & keep alive.
DBD – database description – exchange each LSA, typically on initial topology exchange. So router knows a list of that neighbor known LSA.
LSR – Link State Request
LSU- Link state update.
LSAck – Link State Acknowledge. – confirm msg.
Neighbors States:
Down state - no hello received form the neighbors (more than the dead interval)
Attempt – After sending hello, but before receiving a hello from that neighbor.
Init – received hello packets but did not have any local routers RID. No criteria checked.
2way – received hello packets and its has a routers RID in it. All the criteria passed.
EXStart - DD packets preparation.
Exchange – finished Exchange DD packets
Loading: All DD packets are exchanged and routers are currently sending LSR, LSU and LSAck packets to exchange full LSA.
Full – neighbors are fully adjency. Routing table calculation begin now.
Database exchange without DR (Point to point topoloy)
Down state - no hello msg send.
Init – hello msg send
2way – received hello packets and. All the criteria passed. Neighbors are listed in the neighbors list.
EXStart –after first DD packets sent to 224.0.0.5 DD msg included LSID and LSA sequence no.0x80000001and increment when changes happen.
Exchange: master elected first mater send DD msg responded by slave. When master is finished slave can update msg . Routers know what LSA to send to neighbors what LSA its wants to neighbor to send to it.
Loading : All DD packets are exchanged and routers are currently sending LSR, LSU and LSAck packets to exchange full LSA.
Full State: Every router has the Same LSDB
Database exchange with DR
Down state - no hello msg send.
Init – hello msg send
2way – received hello packets and neighbor relationship with DR and BDR is confirmed with matching allows. Neighbors are listed in the neighbors list.
EXStart –begin when neighbors send first DD packets sent to 224.0.0.6 DR + BDR multicast addressing.
Exchange: master always DR . DR send DD msg of LSA its known to slave 224.0.0.5 when master is finished slave can update DD msg .that master doesn’t have.
Loading : All DD packets are exchanged and routers are currently sending LSR, LSU and LSAck packets to exchange full LSA.
Full State: Every router has the Same LSDB
OSPF neighbors two types:
1. Neighbors ( NBMA Full state refers to the state between DROther and DR or BDR refers 2way state to refers to this relationship between no –DR and BDR neighbors.
2. Fully adjacent (Point to point only two router its fully adjacent)
Each LSA flooded every 30 mins
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