How to determine default gateway? (cisco packet tracer)?

zanmato

I'm doing an activity on cisco packet tracer. I must perform a static route on the said activity. I have a router,switch, and 2 end devices. I already performed IP Addressing and the end devices already has an IP address. How can i determine the default gateway of the end devices?

With 100 hosts I have the address(assignable) range of 180.180.0.1 - 180.180.0.126 prefix /25

satishtech

You must assign the Default Gateway manually to the
end devices , unless you have configured DHCP on the
Router or are running a DHCP Server PC in the LAN.

Maybe this:
Switch#show cdp entry *

zanmato

Hi thanks for the reply. I don't know if this is correct but what i did is:

PC1:

IP Address: 180.180.0.2
Subnet Mask: 255.255.255.128
Default Gateway: 180.180.0.1

PC2:

IP Address: 180.180.0.125
Subnet Mask: 255.255.255.128
Default Gateway: 180.180.180.124

Is this correct?

Codeman6669

your gateway is the IP address of the routers interface that is connected to your LAN.

zanmato

So the one I posted is incorrect? Sorry i'm kinda new to this

satishtech

Two gateways ? Are you trying to run VLAN's
or two seperate interfaces on the Router ?

You say in your PT setup you have a single router
and you are trying to configure a Static Route ?
To what ? The Loopback ?But if it is a single router/switch
setup, pc's can talk to the l0 int.

Are you trying some advanced configuration ?

Chev Chellios

Hi Zanmato,

Which activity is it you are trying in PT out of interest?

As codemann6669 says, your default gateway should be the address of the router
interface your devices are connecting to.

zanmato

Sorry for not elaborating much, I need to perform a static touting that will allow packet to move from one network to another

Here is the topology diagram that i made in CPT:



By using VLSM, I already have the IP Address of those 8 end devices including their subnet masks. But i don't know where to get the Default Gateway to add the IP Address on the routers

crazboy84

Youve got a couple things wrong. it seems like im missing info as far as your assignable address pool but im going with what you have posted so far. First off your subnetting is incorrect fa0/0 and fa0/1 need to be on seperate subnets. You have also used too large of subnets as you have only 126 bits available . You need to be using a /29 as you only need 3 hosts per subnet unless the instructions say otherwise. Remember your default gateway is always the address of the routers port your device is going to. Best practice is to use the first assignable host in a subnet for your default gateway. here is some config that will work in this enviroment.

PC0
IP Address: 180.180.0.2
Subnet Mask: 255.255.255.248
Default Gateway: 180.180.0.1

PC1:

IP Address: 180.180.0.3
Subnet Mask: 255.255.255.248
Default Gateway: 180.180.0.1

PC2:

IP Address: 180.180.0.10
Subnet Mask: 255.255.255.248
Default Gateway: 180.180.180.09

pc3

IP Address: 180.180.0.11
Subnet Mask: 255.255.255.248
Default Gateway: 180.180.180.09

heres your router config your missing.

router 0
en
config t
int fa0/1
ip address 180.180.0.1 255.255.255.248
no shutdown
int fa0/0
ip address 180.180.0.9 255.255.255.248
no shutdown

Take what i have shown you and duplicate it on the other side. You also need to set up your router to router configuration. Let me know if you need assisatance with that. It will need network addresses on both sides and id probobly use a static route for routing purposes. if that doesnt fix it perform a show run on the router and we will be happy to take a look!

zanmato

Thank you for that information! I'm kinda getting it, since now I know that the first assignable/usable host will be the default gateway. It also worked when i performed static route. A question though how many subnet hosts does this have?

crazboy84

zanmato wrote: »

Thank you for that information! I'm kinda getting it, since now I know that the first assignable/usable host will be the default gateway. It also worked when i performed static route. A question though how many subnet hosts does this have?

The default gateway doesnt have to be the first assignable host. That is just generally best practice. On the exam you may encounter a question where they tell you to assign the last assignable host to the default gateway. Some companies also do this although the reasoning escapes me.

The topology you are showing needs 12 subnets and you will need to use VLSM to determine the size of each of thosethose subnets. Remember: subnets are divided by router ports each router to router or router to hosts needs its own subnet.

zanmato

My instructor said use the first usable host as the default gateway for now. I have another problem when configuring router-router. Based on the topology, i have routers that has 2 serial ports:

Router0:
Se0/0/1:
IP Address - 180.180.1.161
Subnet Mask - 255.255.255.252

Se0/0/0:
IP Address - ????
Subnet Mask - ????

What will the Se0/0/0 IP address be? i tried 180.180.1.162 and it says it overlaps the Se0/0/1

EDIT: Nvm i was putting the wrong IP address. Thanks to all who helped! Really appreciate it. All I have to do is pass this to my instructor!

crazboy84

Good luck!

Ltat42a

Here's a good example - the IP address on the Fa0/0 interface is the default gateway for PC0 & PC1. The IP address on interface Fa0/1 is the default gateway for PC2 & PC3.

hth