Routing

DAY 11 - NEED TO FINISH :(

Terminology

• Connected Route (C) = The NETWORK that the interface is connected to

• Local Route (L) = The actual IP address on the interface (with a /32 mask)

Static Routing

Default Gateway, you need to configure a default route which matches ALL possible destinations and is used if a more specific route is not found in the routing table. The default route is the LEAST specific route possible 0.0.0.0 with a mask of 0.0.0.0. (this includes IP's from 0.0.0.0 to 255.255.255.255).

Gateway of last Resort and Static Route

The last resort is usually ALL addresses 0.0.0.0 0.0.0.0 192.168.1.1 whilst a static route is for a specific network.

ATEWAY OF LAST RESORT ip route <destination address> <mask> next hop/or exit interface SW1(config)# ip route 0.0.0.0 0.0.0.0 192.168.1.254 STATIC ROUTE: R1(config)# ip route 192.168.4.0 255.255.255.0 gi0/0

Switches flood frames with unknown destinations (destinations not in the MAC table) Routers DROP packets with unknown destinations.

When a Router looks up a destination address in its routing table, it looks for the most specific matching route. The most specific = longest prefix length (/32 longer than /24 and /24 is longer than /16 etc)

Loopback Interfaces ********** JUST ADDING IN HERE FOR NOW

Loopback Intyerfaces are logical interfaces They allow you to assign am IP address to a router or L3 switch which is noty tied down to a physical interface Because they dont have any physical attributes whaich can fail, they newver do down Loopbacks are logical so they cannot physically be in the same subnet as other devices, so they are usually assigned a /32 subnet to avoid wasting IP addresses Best practise to asige a loopback inetrface to your routers The loopback is commonly used for traffic that terminates on the router itself (mgmnt traffic, VoIP, BGP peereing etc) This provides redundancy if there are multiple paths to the router The loopback is also used to identify the router (Router ID) in OSPF Multiple loopbacks can be configured, this is not common and only done wherer another separate loopback is required for a special use case