Ccna-4-cisco Dynamic Routing

· Dynamic Routing : a route that can be self-adjusted based on network structure or traffic changes

· category :

1. Distance vector Routing Protocol (DV): RIP, IGRP Send routing entry via routing protocol

2, Link State routing Protocol (LS): OSPF, Is-is No routing entries, only by collecting link information to calculate the route

3. Hybrid routing protocol: EIGRP nature is the distance vector routing protocol, but has the function of link state

· Distance Vector routing protocol:

By periodically replicating the routing table to neighboring routers and vector heap

• Features:

1, the Update form: the use of periodic full update (send the entire routing table, as long as the content is updated) and trigger the update in combination with the route update mode

2, Update mode: The use of broadcast format for routing updates (RIPV2 is using multicast)

3. Routing protocols are: RIPv2, RIPV1, and IGRP (both deactivated)

4, EIGRP and BGP (large network core) belong to the Advanced DV Protocol, learning Path more approach DV, but they have many features of LS (such as trigger update, multicast update, etc.)

• The process of obtaining a path:

The router chooses the best path to reach the destination address from the source information collected (forwarding, replicating the routing table)

• The generation of loops:

Slow convergence tends to cause inconsistent routing information, and routers incorrectly assume that the route sent is also the correct route, resulting in a loop

• Loop resolution (1, 2, 4 is default, 3, 5 need to be configured yourself):

1, Maximum hop count (max-hop): Specifies the maximum hop count to prevent the routing loopback

2. Horizontal split (split Horizon): will not accept routing information that is communicated by itself

3. Route poisoning: The router marks the hop count of the routing information as Infinite. The wrong route is marked as down (poisoned), which in turn can be determined to be unreachable when it is issued. Compared to a horizontal split, it is quicker to determine whether the route is up or down.

4. Keep the expiration timer: The router marks the record as possibly down in hold-down time so that other routers can recalculate the changes in the network structure

5. Trigger the update

· Rip:

Also known as the distance Vector protocol, a unit of distance (that is, the number of routers that are routed through) is used by the gateway that the packet passes through, and more than 15 hops are unreachable. Routers are updated every 30 seconds (that is, every 30 hops update) up to 16 paths with the same hop count for load balancing

· RIP's metric is based on hop count (hop count), and metric is 16 for unreachable.

· RIP timer:

1. Routing Update timer: Set the time interval (default 30s) for routing periodic updates, sending a full routing table copy to the neighbor

2, the route failure timer: Determine a route to become a failure route waiting time (default 180s), once become a failure route, the update message will be sent to all neighbors, notify themselves failure (the time to determine the route failure)

3. Keep the expiration timer: Set the routing information to be suppressed time (default 180s) when an update packet indicating that a route becomes unreachable route is accepted,

The router goes into a failed state, continues to a better measure of the update packet being accepted or the timer expires. (The time that the failed route exists in the router)

4. Route Refresh Timer: Sets the time interval (240s) that routes become invalid routes and removed from the routing table

· Configuration of RIP routes:

Show IP Protocol View Gateway

Clear IP route * clearly routing table

• Modify RIP version 2:

Router (config) #router rip

Router (config-router) #version 2

Router (config-router) #no auto-summary

R1:

Router RIP

Network 192.168.3.3 150

R2:

Router RIP

Network 192.168.2.3 150

• Hybrid routing Protocol (EIGRP):

The most typical balanced hybrid routing protocol, which combines the advantages of two routing protocols, the distance vector and link state, uses the Flash update algorithm to achieve the fastest network convergence in all routing protocols (convergence)

Characteristics

1, the use of occasional updates (RIP is updated regularly), that is, only when the router changes the measurement standard or topology changes when the sending part of the update route.

2. The update entry contains a mask (no class routing protocol), supports VLSM, and supports discontinuous subnets.

3, with the same autonomous system is not fixed (refers to the same management domain, is a management concept, not fixed) the number of EIGRP and IGRP (both have the same measure, that is, the standard is the same measure of link quality is the same), can seamlessly exchange routing information.

function

1, through the protocol related modules support Ip,ipx,appletalk (that is, only one network protocol is required to support different networks)

2, no-class routing protocol (that is, with a mask to differentiate the network number), (all masked operations) support VLSM and CIDR

3, support summary and discontinuous network

4, the Effective Neighbor Discovery (RIP uses UDP, because there is no confirmation mechanism to send is not reliable, and EIGRP will be sent before the confirmation can establish a neighbor relationship to send a routing protocol)

5, based on reliable Transmission Protocol (RTP) communication, to ensure the delivery of reliable update package.

6. Optimal path selection based on dispersion update algorithm (DUAL)

• Neighbor Discovery:

· EIGRP routers exchange routes with each other and must be neighbors, establishing a neighbor relationship to meet three points:

1. Receive a Hello or ACK (the neighbor must return an ACK after receiving the message)

2. Match as number (only routes that belong to the same admin domain have the same as number can be neighbors)

3. Same metric (the parameters of the EIGRP path must be the same)

• noun Explanation:

1. Feasible Distance: Neighbor Report metrics + Report neighbor metrics for this route (A-b-c is the best path)

2. Distance value reported: Neighbor report arrives remote network metric (A-D-E-C)

3, Successor: the best route to the remote network, the route used to forward the service, there is a routing table (that is, b)

4, feasible successor: is a path, and than the feasible distance, considered to be a backup route (that is, d)

0a--5--0b--7--0c

| -------Road 1----→|

|2↓|5↑

| -------Road 2----→|

0D ————— 6 ————— 0E

• Reliable transport protocol: When EIGRP sends multicast data to a neighbor and does not receive a response from a neighbor, the Tan sends the same data, and after 16 times there is no answer, the neighbor is declared extinct, that is, reliable multicast.

• Dispersion update algorithm: Dual in no alternative path sometimes for EIGRP to quickly ask for neighbor lookups.

· Comparison of EIGRP and IGRP:

• Same point:

1. Similar metric calculation

IGRP:METRIC=BW (min) +dly (sum)

EIGRP:METRIC=256 (2 of 8, or more than one byte) x[bw (min) +dly (sum)]

2, all support equivalent load balancing and not equal load balance

• Different points (Igrp is eliminated by EIGRP):

1, support VLSM and discontinuous subnets (IGRP routing protocol itself is the enhancement and expansion of RIP, adapt to the network and increase the measure value)

2, Support manual summary

3, flash update, Faster convergence time (IGRP and RIP as replication routing table send)

4, only to change the entry update, the use of less network resources

· Configuration of EIGRP:

R1 (config) #router EIGRP 100

R1 (config-router) #no au

R1 (config-router) network 192.168.1.0

R1 (config-router) network 1.0.0.0

R2 (config) #router EIGRP 100

R2 (config-router) #no au

R2 (config-router) network 192.168.1.0

R2 (config-router) network 2.0.0.0 Main class Notice

R2 (config-router) network 192.168.2.0 0.0.0.255 precise notice

R3 (config) #router EIGRP 100

R3 (config-router) #no au

R3 (config-router) network 192.168.2.0.0 0.0.0.255

R3 (config-router) network 3.3.3.0 0.0.0.255

· OSPF Open Shortest Path First:

• Is an open standard, the use of the shortest Path first algorithm (shortest), which is computed, is a link-state routing protocol, because it is computed, so the LSA is forwarded between the routers, not the routing entry.

• Information tracking:

1. Neighbor information (same as EIGRP)

2, all the routers in this area, know all the network segment status in the area

3, the best path to reach the target network

· Three tables of the OSPF protocol:

1. Neighbor Table: Neighbor Router Information

2. Topology table: Also called link state database, different from EIGRP, all link state (LSA) advertisements stored

3. Routing table: the best path to reach the target network

· The area concept of OSPF:

1, the backbone of the region (area 0), is stipulated

2. General area

Note that all conventional areas must be connected to the backbone area

The setting of the zoning can limit the change of information in the region, such as area1 information changes will not affect area0 and area2. Setting up the backbone area to connect to the regular area and forwarding is to prevent the loop from being generated, ensuring that only a fixed path can be transmitted.

· DR/BDR Election rules:

1, when the election dr/bdr to compare the priority in the Hello packet, the highest priority for the DR, the second high for the BDR. The default priority is 1. In the case of the same priority level, the highest Rid,rid rank is the DR, and the second high is the BDR. When you put

When the priority is set to 0, the OSPF router cannot become a dr/bdr and can only be drother.

2. After the DR/BDR election is completed, Drother only and dr/bdr form the neighboring relations. All routers will multicast Hello packets to address 224.0.0.5 so that they can track the information of other neighbors, that is, DR flooding LSU to 224.0.0.5;d Rother only multicast LSU to Alldrouter address 224.0.0.6, only dr/bdr listens to this address.

3. Dr and BDR will not change in the case of a restart

• When the priority of the Hello packet is the same, the election by router ID is required:

· Router ID:

The identification number of the router in OSPF

Default: The maximum active interface IP address after the OSPF process is enabled

Manual configuration is the highest priority and then the loopback interface is better than the physical interface, then the physical interface is larger than the physical interface small

Router ID is a IPv4 address, can be set by hand. The Router ID has a large preference for exchanging LSA information.

Configuration:

R1 (config) #router OSPF 10

R1 (config-router) #router-id 1.1.1.1

R1 (config-router) #network 192.168.1.0 0.0.0.255 area0

R2 (config) #router OSPF 100

R2 (config-router) Router-id 2.2.2.2

R2 (config-router) network 192.168.1.0 0.0.0.255 area0

Ccna-4-cisco Dynamic Routing