To establish static routes, use the ip route command in global configuration mode. To remove static routes, use the no form of this command.
ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name] [permanent | track number] [tag tag]
no ip route prefix mask
Example:
ip route 1.1.1.0 255.255.255.0 serial 0/0
ip route 2.2.2.0 255.255.255.0 3.3.3.3
9
………………………………………………………………………………………………………
Static route ≠ default route
default route: route of last resort, the last route tried by a router when all other routes fail
When use “showip route” the entry with “*”
static route: user-defined routes that cause packets moving between a source and a destination to take a specified path
When use “show ip route” the entry start with “S”
Sometime we may use static route to define a “default route” on router
10
………………………………………………………………………………………………………
Configure a default route by using “ip route” command
ip route 0.0.0.0 0.0.0.0 {ip-address | interface-type interface-number [ip-address]}
Example:
ip route 0.0.0.0 0.0.0.0 serial0/0/1
ip route 0.0.0.0 0.0.0.0 1.1.1.1
11
………………………………………………………………………………………………………
Interior Routing Protocol
Characteristics of distance vector protocols:
Routers share copies of routing tables
Distance metric can be based on hops, cost, bandwidth, speed, delay or reliability
Vector is the address of the next hop along a route
Ex. RIP, EIGRP
12
………………………………………………………………………………………………………
Distance Vector Routing Protocols
•Distance – how far?
•Vector – in which Direction
•Router pass periodic copies of routing table to neighbor routers and accumulate distance vectors
13
………………………………………………………………………………………………………
Interior Routing Protocol
Characteristics of link-state protocols:
Full database of distant routers and interconnections
Link-state advertisements
Topological database
SPF algorithm
Ex. OSPF, IS-IS
14
………………………………………………………………………………………………………
Exterior Routing Protocol
The Internet is divided into autonomous systems
AS: a set of networks controlled by a single administration using the same internal routing policy
Each ISP is an AS
15
………………………………………………………………………………………………………
Exterior Routing Protocol
Interior gateway protocols (IGPs) exchange routing information within an AS or individual organization
Exterior gateway protocols (EGPs) exchange routing information between autonomous systems
16
………………………………………………………………………………………………………
Exterior Routing Protocol
Each AS uses dedicated border gateway routers to route packets across the Internet
17
………………………………………………………………………………………………………
Exterior Routing Protocol
ISPs use exterior routing protocols to forward or control local and/or transit traffic
Exterior protocols enforce policies and support reliability
18
………………………………………………………………………………………………………
Exterior Routing Protocol
Configuring Border Gateway Protocol (BGP):
Configure the AS number
Identify ISP neighbor router
19
………………………………………………………………………………………………………
Routing Information Protocol (RIP)
Interior Routing Protocol
RFC 1058
Distance vector using hop count metric
Updates every 30 seconds
20
………………………………………………………………………………………………………
Routing Information Protocol (RIP)
RIP version I – Classful Routing Protocol
RIP version II – Classless Routing Protocol
Use Hop Count as Cost (Max. 15 Hops)
21
………………………………………………………………………………………………………
•Slow convergence in Router C
•Inconsistent Routing Entries
33
………………………………………………………………………………………………………
Router C learns the best path to 10.4.0.0 is through Router B
34
………………………………………………………………………………………………………
Router B update from Router C
•Router A update from Router B
•Incorrect Hop Count in all Routing Tables
35
………………………………………………………………………………………………………
•When there is a packet for Network 10.4.0.0, a loop between Router B and Router C is occurred.
………………………………………………………………………………………………………
Techniques to eliminate Routing Loop Problem
Define Maximum Hop Count
Triggered Update
Split Horizon
Split Horizon with Poison Reverse
Hold-down Timer
37
………………………………………………………………………………………………………
Triggered Updates
Network 10.4.0.0 is unreachable
Network 10.4.0.0 is unreachable
Network 10.4.0.0 is unreachable
Routers send update immediately when its routing table occurs.
38
………………………………………………………………………………………………………
Hold down Timers
Network 10.4.0.0 is unreachable
Network 10.4.0.0 is Down
Then Back Up
Then Back Down
Update after Holddown timer
Update after Holddown timer
41