Static routes, summary static, default static

rackemup

Hello All,


Long time lurker here, first post.


Just finished a lab regarding these. From my understanding...


1) Static routes - "hardcoded" routes pointing to a single specific network (must be configured correctly in RETURNING paths for pings to work!)


2) Summary static routes - If multiple lines of DIFFERENT SPECIFIC networks point to the same exit interface or next hop, then a SUMMARY static route may be used to reduce cpu overhead and the size of the routing table.


3) Default static route - Help please? (maybe I just need a break, but I'm having trouble wrapping my mind around this one)

networker050184

A static default route is used to send everything that you don't have a destination for in the routing table (depending on ip classless of course). For instance when you connect to the internet from home, your router doesn't have a destination network for every site on the internet. It simply has a default route pointing to another router where it will eventually get to a router that has a specific route for said destination. It would be something like "ip route 0.0.0.0 0.0.0.0 [next hop/exit interface] for a static default.

peanutnoggin

rackemup wrote: »

3) Default static route - Help please? (maybe I just need a break, but I'm having trouble wrapping my mind around this one)

A default static route is one in which you will send traffic to if the router cannot find a route to a network in it's routing table.

Example... RTR1's routing table has the network 192.168.1.0 /24 connected and route 172.16.10.0 - configured as a static route. A client on the 192.168.1.0 network wants to send traffic to 10.10.10.5. RTR1 does not have a route to 10.10.10.5 and therefore would have to send to its "default route". Usually your default route is going to be to your ISP (depending on your setup). You can configure it by typing the following:

rtr1(config)#ip route 0.0.0.0 0.0.0.0 IP_OF_NEXT_HOP

The first 0.0.0.0 means any network
The second 0.0.0.0 means any subnet
The last IP is the next hop IP address.


I hope this helps.

rackemup

So a static default route is akin to saying, "I don't know the route, but I'll send this packet down the line through this default route and let the next router worry about getting the job done."


I seem to picture a static default route as the last line in a list of "static statements" (so to speak) like ACLs.


Therefore...

Static routes are very granular when routing to destination.

Summary static routes are for cases of "ad nauseam."

Default static is a "last chance hope" to send to destination.



Thanks for the clarifications - much appreciated.

networker050184

rackemup wrote: »

So a static default route is akin to saying, "I don't know the route, but I'll send this packet down the line through this default route and let the next router worry about getting the job done."


I seem to picture a static default route as the last line in a list of "static statements" (so to speak) like ACLs.


Therefore...

Static routes are very granular when routing to destination.

Summary static routes are for cases of "ad nauseam."

Default static is a "last chance hope" to send to destination.



Thanks for the clarifications - much appreciated.

Thats the gist of a default route. It can be static or dynamic. Just wanted to point that, not sure if you understood that part or not.

Aldur

networker050184 wrote: »

Thats the gist of a default route. It can be static or dynamic. Just wanted to point that, not sure if you understood that part or not.

Good point here. You can create a default static route or you can receive a dynamic default route via a routing protocol, such as BGP or OSPF.

rackemup

So progressing forward, my updated understanding is...

There are two types of default routes:

1) Default dynamic route
-Sent by another router via a routing protocol
-Cannot be created locally

2) Default static route
-Created locally on router
-Cannot be sent by another router


I continued practicing these in another lab...

R2---R1---Sw1---PC1

OBJECTIVE:
R2 ping PC1 using STATIC route
PC1 ping R2 using DEFAULT STATIC route

I couldn't get this to work.

I ended up creating a default static on both R1 and R2. I know this isn't a true solution in case I added another spoke to R1.

Rather than ask for what I did wrong and post configs, I tried to troubleshoot it myself.

debug ip icmp (forgot to copy the output!)

I can't let this static route issue go until I ultimately achieve a ping from PC1 to PC2 and vice versa.

PC2---Sw2---R3---(R2)---R1---Sw1---PC1

I'm about half-way there on the theory, though I'm at a dead stop on the practical side of things.

Suggestions, please?

tim100

rackemup wrote: »

I can't let this static route issue go until I ultimately achieve a ping from PC1 to PC2 and vice versa.

PC2---Sw2---R3---(R2)---R1---Sw1---PC1

I'm about half-way there on the theory, though I'm at a dead stop on the practical side of things.

Suggestions, please?

Lets say the Sw1---PC1 network is 192.168.10.0/24 and the Sw2---PC2 network is 192.168.20.0/24

Sw2:
ip route 192.168.10.0 255.255.255.0 (R3 IP)

R3:
ip route 192.168.10.0 255.255.255.0 (R2 IP)
ip route 192.168.20.0 255.255.255.0 (Sw2 IP)

R2:
ip route 192.168.10.0 255.255.255.0 (R1 IP)
ip route 192.168.20.0 255.255.255.0 (R3 IP)

R1:
ip route 192.168.10.0 255.255.255.0 (Sw1 IP)
ip route 192.168.20.0 255.255.255.0 (R2 IP)

Sw1:
ip route 192.168.20.0 255.255.255.0 (R1 IP)

PC1 - default gateway is Sw1
PC2 - default gateway is Sw2

APA

rackemup wrote: »

I can't let this static route issue go until I ultimately achieve a ping from PC1 to PC2 and vice versa.

PC2---Sw2---R3---(R2)---R1---Sw1---PC1

I'm about half-way there on the theory, though I'm at a dead stop on the practical side of things.

Suggestions, please?

Are those switches L2 switches or L3 switches? (e.g what are the PC's using as default gateways... the switches or R3 and R1 respectively...)

Quickly though assuming the PCs are using R1 and R3 as respective gateways.... you should have it setup like this....

[Router1]

ip route (Router 3 Network) (Netmask) (next-hop to Router 2)

[Router 2]

ip route (Router1 Network) (Netmask) (next-hop to Router 1)
ip route (Router3 Network) (Netmask) (next-hop to Router 3)

[Router 3]

ip route (Router 1 Network) (Netmask) (next-hop to Router 2)


Remebering that the directly connected interfaces on each Router will already be in the RIB... because... they are connected (as long as the interfaces are UP of course)!


The above will use R2 as the transit point between each networks thus the specific static routes for the networks that each R1 and R3 home...... and then R1 and R3 can just have the explicit static point to the othersides network......

A static default route pointing to R2 for both R1 and R3 would be alot easier for you to grasp this concept I think. As then I would ask you to hang another network of R1 and then tell me where you would need to configure the route to allow connectivity from PC2 towards the new network behind R1.

Does this clear the air for you a little more?