EIGRP of Dynamic routing protocol

EIGRP(enhanced Interior Gateway Routing Protocol )

Enhanced Internal Gateway Routing protocol

Features of EIGRP:

· EIGRP is a Cisco Private routing protocol that employs the DUAL(diffusion update algorithm).

· EIGRP belongs to IGPand is the Hybrid protocol, based on IP Pro.

• Multicast, unicast update, multicast address 224.0.0.10

• Supports load balancing with equal / unequal prices.  

• Support VLSM, manual summary.

• Support for multiple network protocols (ip/ipx).

EIGRP maintains 3 tables for various protocols:

1) Neighbor Table:

Save the IP address of a direct-attached neighbor to ensure that the direct neighbors can communicate in two directions.

2) Topology Table:

All routes to the destination address are stored in the topology table.

3) Routing Table:

Select the best route to the destination address from the topology table to put in the routing table.

Dual algorithm:

Diffusion update algorithm, also called dispersion update algorithm

AD (notification distance)-------------the metric of the destination that the neighbor advertises

FD (feasible distance)-------------the metric of the router's destination

Successor routing-------------routes with optimal metric values

Feasible successor routing-----Qualifying sub-optimal routing

Sub-optimal routing becomes the condition of the feasible successor: also called the feasibility condition

FD of Best route > AD's Second best route

(successor)

In EIGRP, the router chooses the optimal route from the topology table to a particular destination, also known as the successor route, into the routing table, and once the optimal route is down, EIGRP will immediately find the Feasibel successor route from the topology table and upgrade it to the optimal route. And put in the routing table, without having to calculate, so as to improve the speed of convergence.

If the successor route in the current routing table is down and there is no backup route in the topology table, EIGRP sends a query packet to all direct-attached neighbors for the diffusion query.

RTP (Reliable Transport Protocol) Reliable Transport protocol

Used to manage the delivery and reception of EIGRP messages for reliable transmission.

The so-called reliable transmission refers to the delivery of guaranteed and the message is ordered to send.

Common messages in EIGRP:

Hello: For neighbor Discovery and recovery. (multicast)

Update: pass-through routing updates that contain only the required route entries, use unicast (p-to-p) When an update is issued for a specified router, and multicast when an update is made for more than one router. (MA)

Query: Send Inquiry message (UNICAST) when feasible successor is not found

Reply: Respond to query messages. (Unicast)

ACK: Used to confirm update/query/reply (Unicast)

Reliable packets:update/query/reply

Unreliable packets:hello/ack

· Hello Address = 224.0.0.10

· Hello Timer

5S:≥T1 (1.544Mbps) also has a random time difference to prevent updates from synchronizing

60s:

· Hold timer = 3 * Hello Timer

• The necessary conditions for forming a neighbor relationship

1, the two sides K value consistent.

2, as num consistent.

3, authentication must be consistent.

• Even if the Hello Timer & hold timer on both sides is inconsistent, a neighbor relationship can also be formed.

· SRTT (Smooth round-trip time) average round trip times:

From sending 3 reliable packets to the other party in response to the ACK time. (MS)

· RTO (retransmission TimeOut):

A timer that re-passes the timeout.

· Queue count queue number of messages that are still queued for delivery

16 Retransmission mechanisms:

In Egirp, if a router sends a reliable message to a neighbor, it needs a neighbor to respond to an ACK message, and if the neighbor does not return an ACK, it will retransmit 16 times to the neighbor, resetting the neighbor if the neighbor has not responded.

The metric value of EIGRP is calculated:

The calculation of the metric value of EIGRP can use up to five parameters, which in fact usually only uses two.

Formula:

EIGRP Metric = 256* (107/BW+DLY/10)

Attention:

1. Bandwidth takes the minimum bandwidth value on the routing path

2. Delay is the sum of the delay of the incoming interface in the direction of taking the route

Bandwidth and latency for several common interfaces:

Interface BW (Kbps) DLY (μsec)

Ethernet 10000 1000

FAST 100000 100

G0 1000000000 10

Serial 1544 20000

Loopback 8000000 5000

In the complete calculation formula, each parameter is also multiplied by its own weight value:

k1= Bandwidth bandwidth ( minimum bandwidth between source and destination) 1

k2= load loading (maximum load between source and destination) 0

k3= delayed delay ( sum of delay between source and destination) 1

k4= Reliability Reliability (minimum reliability between source and destination) 0

K5=MTU (minimum MTU between source and destination) 0

Basic Configuration

R2(config)#router eigrp 90

R2(config-router)#network 12.1.1.0 0.0.0.255

R2(config-router)#network 2.2.0.0 255.255.0.0　（正/反掩码皆可）

R2#show ip protocols 

R2#show ip eigrp interfaces 

R1#show ip eigrp neighbors 

R1#show ip eigrp traffic

R1#show ip eigrp topology             //只能显示successor和feasible successor

R1#show ip eigrp topology all-links   //可显示拓扑表中的所有条目

Testing different as Num can build neighbors.

Test Hello/hold Timer inconsistency can build a neighbor.

• Modify Hello/hold Timer

R1(config-if)#ip hello-interval eigrp 90 60

R1(config-if)#ip hold-time eigrp 90 180     //记住，hold-time时间是给邻居用的

show ip eigrp interface detail s1/0   //查看接口的hello时间

• Modify the K value

R3(config)#router eigrp 90

R3(config-router)#metric weights 0 1 1 1 0 0

Automatic summary >

Eigrp turns on auto-summary by default, which means that routes are automatically aggregated into main classes when they cross different network boundaries.

router eigrp 90

  no auto-summary  //本命令关闭自动汇总

Manual Summary >

int s1/0

  ip summary-address eigrp 90 20.1.4.0 255.255.252.0  //只能在路由流向的出接口作手工汇总

The local router generates a special route, the ad value for this special EIGRP rollup route is 5

D 20.1.4.0/22 is a summary, 00:00:02, Null0

Features of the summary:

1, the local must have a detailed route, only from the interface to make a summary of the summary route.

2. Until the last route of the detail disappears, the rollup disappears.

3, the metric value of the summary route will take the minimum metric value

4. A special route to the null interface is generated on the router that makes the rollup, and the route to the NULL0 interface is used to prevent the loop

D 2.0.0.0/8 is a summary, 00:02:30, Null0

5, only the local routes are summarized into the main class, for the received routes do not summarize, issued directly.

show ip route 172.16.0.0 255.255.0.0  可以看到指向Null0接口的特殊汇总路由的管理距离

Equivalent load Balancing

· EIGRP can do equivalent load balancing, or do not load balance. By default, only the equivalent is done.

· EIGRP supports load balancing of 4 paths by default, with a maximum support of 16.

show ip protocols    //可查看EIGRP的负载均衡路径数

router eigrp 90

  maximum-paths 6（最多16条）   //本命令改动负载均衡的路径数

If the metric of multiple routes are unequal, the equivalent load balancing can be achieved by modifying the metric value in the following two ways:

1. Modify EIGRP interface Bandwidth or delay

• By modifying the bandwidth or delay of the interface, you can reach the target of altering the metric value of the route.

• Change the entry in the routing direction.

• When the delay is changed, it is changed in 10 units. For example, to change the interface delay to 2000usec

You want to:

  int e0/0

    delay 200   //输入的值默认会*10，是以10为单位来改的

  show interface s1/0  使用这条命令可以看到接口的带宽和延迟

Example one:

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As shown in: After running EIGRP, R2 can learn two 3.3.3.0 routes, one from R3 and the other from R1.

show ip eigrp topology detail-links 

P 3.3.3.0/24, 1 successors, FD is 409600, serno 6

        via 23.1.1.3 (409600/128256), Ethernet0/0

        via 12.1.1.1 (2809856/2297856), Serial1/0

If you want to achieve equivalent load balancing, you can modify the delay of the e0/0 interface to achieve

int e0/0

  delay 9476      //将接口延迟改为94760μS

show ip route

     3.0.0.0/24 is subnetted, 1 subnets

D       3.3.3.0 [90/2809856] via 23.1.1.3, 00:00:08, Ethernet0/0

                [90/2809856] via 12.1.1.1, 00:00:08, Serial1/0

2, the offset list >

With this thing, you can also change the metric value of different routes to be used for load balancing

Access-list 1 Permit 1.1.1.0 0.0.0.0

Router EIGRP 90

Offset-list 1 in 3 Serial 1//This command can only add metric value on the original basis

(Original metric + 3)

Router EIGRP 90

Offset-list 0 in 3 Ethernet 0//Metric value of all routes coming in from the E0 interface plus 3

(0 means all networks)

Example two:

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As shown in: After running EIGRP, R2 can learn two 3.3.3.0 routes, one from R3 and the other from R1.

R2#sh ip eigrp topology detail-links 

P 3.3.3.0/24, 1 successors, FD is 409600, serno 6

        via 23.1.1.3 (409600/128256), Ethernet0/0

        via 12.1.1.1 (2809856/2297856), Serial1/0

If you want to achieve equivalent load balancing, you can use the offset list on R2 to increase the metric value of the 3.3.3.0 routes that come in the e0/0 interface.

R2(config)#access-list 1 permit 3.3.3.0

R2(config-router)#offset-list 1 in 2400256 e0/0

R2#show ip route

     3.0.0.0/24 is subnetted, 1 subnets

D       3.3.3.0 [90/2809856] via 23.1.1.3, 00:00:24, Ethernet0/0

                [90/2809856] via 12.1.1.1, 00:00:24, Serial1/0

Load balancing at unequal prices

By default, EIGRP supports only equivalent load balancing, and the following command enables unequal-price load balancing.

The following command can be used to set a variable, and then use this variable multiplied by the current successor Route FD value can be a reference value

router eigrp 90

  variance 2  

As long as the feasible successor route in the current topology table satisfies the following conditions, it can be placed in the routing table to achieve unequal price load balancing.

FS's fd u*successor ' s FD (reference value) U value is the variable value, set by the Variance command (1-128)

Note: The premise of doing not equal load balancing is that routing must first become feasible successor, otherwise it will not be used for load balancing

Cases:

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As shown: After running EIGRP, you can learn two 13.1.1.0 routes on R2, one becomes successor, and one becomes FS.

show ip eigrp topology   

P 13.1.1.0/24, 1 successors, FD is 2195456

        via 23.1.1.3 (2195456/2169856), Ethernet0/0

        via 12.1.1.1 (2681856/2169856), Serial1/0

Unequal-price load balancing can be achieved by setting the variance variable

router eigrp 90

  variance 2

show ip route

     13.0.0.0/24 is subnetted, 1 subnets

D       13.1.1.0 [90/2195456] via 23.1.1.3, 00:00:13, Ethernet0/0

                 [90/2681856] via 12.1.1.1, 00:00:13, Serial1/0

• By default, the EIGRP protocol itself consumes up to 50% of the interface's reference bandwidth.

If bandwidth is not set using bandwidth, the interface default bandwidth is used.

• Use the following command to change the bandwidth value that EIGRP consumes

int s1/0

  ip bandwidth-percent eigrp 90 200   后面的参数为百分比

                            （BW * 200%）

This command can only show run interface see

Note: The bandwidth seen in show interface is called the reference bandwidth, which is not the actual bandwidth of the interface, the actual bandwidth of the interface is determined by the clock rate, and the reference bandwidth is only used to calculate the metric value or some other application.

only supports MD5 and does not support clear text authentication

The first step:

key chain R2　                （本地有效）定义KEY库名为R2

  key 1                       （两端一致）定义KEY号为1

    key-string cisco           定义KEY值为cisco

Step Two:

int s1/0

  ip authentication key-chain eigrp 90 R2  //在接口下指定使用哪个密码库

Step Three:

int s1/0

  ip authentication mode eigrp 90 md5  //开启认证 

show key chain 

debug eigrp packet

R2(config-keychain-key)#Accept-lifetime 04:00:00 jan 2006 infinite 定时接收

R2(config-keychain-key)#Send-lifetime 04:00:00 jan 2006 04:01:00 jan 2006 定时发送

R2(config-keychain-key)#Send-lifetime 04:00:00 jan 2006 duration 300  有效期300S

On a WAN link, EIGRP's proliferation query mechanism may result in queries that are too large or even unnecessary to consume extra bandwidth.

• The following two ways to limit the query scope for EIGRP:

　1) Summary use route rollup to resolve

· The query for EIGRP has the following characteristics:

The query is propagated only if there is an exact matching detail entry in the routing table.

Otherwise, it responds directly to the "network unreachable".

　2) Stub

• The remote router is configured as a stub router by command, and the stub router sends a status of information to all neighbors, and the other routers will not send queries to the stub router.

R1：

router ei 90

  eigrp stub (默认通告直连＆汇总）

The parameters of the stub command are described:

eigrp stub connected     //通告直连路由

eigrp stub summary       //通告汇总路由

eigrp stub redistributed //通告重分布的路由

eigrp stub static        //通告静态路由

eigrp stub receive-only  //只接收不通告

eigrp stub leak-map      //路由泄露

If the stub route wants to pass the self-learned route to the next router, it needs to use the Leak-map

Example: As shown, R1 is the stub router and now wants to pass its own direct-attached routes, summary routes, and 172.16.1.0 routes to R2

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R1：

access-list 1 permit 172.16.1.0

route-map CISCO

  match ip add 1

router eigrp 90

  eigrp stub connected summary leak-map CISCO

SIA (Stuck in Active) card in Active state

When the router does not receive a response from the neighbor within three minutes, it considers that the route has entered the SIA state, and the neighbor relationship is reset.

• Common causes of Sia:

1) query scope is too large

2) The router is too busy to answer the query.

3) Poor link quality between routers, resulting in the loss of query packets.

4) Some unidirectional links fail.

router eigrp 90

  timers active-time [2|disable]

(SIA timer, which defaults to 3 minutes, resets the neighbor relationship for more than 3 minutes to avoid the card in Active state)

Passive interface >

· An interface can also be set as a passive interface in EIGRP

• The passive interface will not receive or send. Therefore, it is impossible to establish a neighbor relationship with the peer router at all.

router eigrp 90

  passive-interface s1/0

Horizontal Division >

The default in EIGRP is also to open horizontal split

int s1/0

  no ip split-horizon eigrp 90   //在接口上使用这条命令可以关闭水平分割

You can set the maximum hop count for available routes on the EIGRP router.

If a router receives a route that passes more than the maximum number of hops it has set, the route will not be passed.

is 100 by default and can be modified to 255

router eigrp 90

  metric maximum-hops 255

show ip protocol  本命令可查看

1) Redistribute Static:

ip route 0.0.0.0 0.0.0.0 serial 0

router eigrp 90

  redistribute static          (默认是按静态路由出接口类型计算Metric）

2) Network 0.0.0.0:

ip route 0.0.0.0 0.0.0.0 serial 0（写下一跳不行，必须写接口）

router eigrp 90

  network 0.0.0.0

3) IP default-network:

In the global mode:

ip default-network 192.168.1.0   //这样就可以把这条路由下发给其它的路由器当做默认路由了

Use this command to meet the following conditions:

1, the interface IP address must be the main class, cannot be a subnet

2, the interface must be declared in EIGRP

3. The main class network number of this interface must also be written when using the command

Note: EIGRP also has the default-information command, but this command is not used to distribute the default route, it is used to determine whether the router will accept the default route, or whether to pass the default route. And only the default route issued by the IP default-network command works.

This article is from the "Ricky Technology Blog" blog, make sure to keep this source http://r1cky.blog.51cto.com/10646564/1774644

EIGRP of Dynamic routing protocol