Secondary Command on Interface

[Mridul72]

On Router 1

interface GigabitEthernet0/0/0

Router(config-if)#ip address 10.10.30.1 255.255.255.0

Router(config-if)#ip address 10.10.20.1 255.255.255.0 secondary

Router(config)#ip route 0.0.0.0 0.0.0.0 10.10.20.2

On Router 2

Router(config-if)#ip address 10.10.20.2 255.255.255.0 secondary

On PC 10.10.30.2

Questions:-

1:-Is this scenario correct

2:-What is the use of secondary command

3-What it do ,How it will work

4:-Will it cause any issue if I got two service provider like on router 1 at gig0/0/1 i have configured anothier ip then what will both connectivty will be fine.

5:-Please Explain this

This scenario is used in my office please help me in understanding this.

[Mark Malone]

whats connected to router g0/0/0 is it another ISP connection ?
secondary addresses are used for migration mostly but can be used for other circumstances depending on setup

Looks like all unknown traffic is sent to airtel router through default route maybe internet traffic only but all LAN network is on 10.10.30.x network connected to the other router maybe its a business MPLS or something , wheres the routing for that ? is there anymore defined routes seems like were missing info here to be able tp get the full picture

[Mridul72]

router g0/0/0 is my location and the router which is conncted via switch is isp connection 

In this scenario

I got one router at my location in which there is only one port available by which my LAN is running but i need to connect to WAN so on same interface i just gave secondary ip and the WAN connection of Airtel i landed on switch 

This is the scenario

[Mark Malone]

why are you using secondary addresses here , why not just use IGP routing like EIGRP or OSPF between the routers and route properly
secondary addresses as i said are mostly for migration purposes to new subnets when old subnets are in place , you could use EIGRP and advertise the networks locally and create an EIGRP neighbor between the routers so each router knows about each other and its paths