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Mashal
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Subnet Routing problem!!!

Tue Jul 28, 2015 2:49 pm

I have an interface with a 10.10.1.1/24 ip
and another interface with a 10.10.1.253/30 ip and i want to make a route between them!!! somebody help please!!!
ive configured the routing table on the client side and they see 10.10.1.253 but they cant see 10.10.1.254 thats on the other side!!
 
Ape
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 3:19 pm

Hi,

you won't be able to get this working with plain routing because 10.10.1.252/30 is a subnet of 10.10.1.0/24.
If you don't need the whole /24 range, you could configure 10.10.1.1/25, now 10.10.1.0/25 and 10.10.1.252/30 are really different nets between you can route.

Ape
 
Mashal
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 3:42 pm

thanx but can u reference me to a text where i could study more complicated routing to sort this with out touching the 10.10.1.0/24 subnet?
 
KBV
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 3:47 pm

Read about the Direct and Indirect delivery of IP packets
 
Mashal
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 3:50 pm

plus i tested changing it to /25 still get no ping reply from 10.10.1.254 :(
 
Ape
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 3:52 pm

Hi Mashal,

I'm afraid, without changing one of your network addresses / subnet masks you really won't get this working. This is the fundamental working of IPv4 networks.
You must create a setup, where the network address space you want to route to, is not contained in the originating network address space.

Have a look at:

https://support.microsoft.com/en-us/kb/164015
https://en.wikipedia.org/wiki/Classless ... in_Routing

These were the first english resources I found googling it.

If you want to search by yourself, search for "IPv4 subnetting", "CIDR IPv4 explanation".
plus i tested changing it to /25 still get no ping reply from 10.10.1.254
You need to change the subnet mask on every device, not only the router!
Second, your remote device in the /30 net must know a route back to your /25 net. If you can't ensure this, youse NAT on the interface which is connected to the /30 net.

Ape
Last edited by Ape on Fri Aug 21, 2015 1:10 pm, edited 1 time in total.
 
Mashal
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 3:54 pm

the confusing thing is that mikrotik says that
"By default forwarding decision is based only on the value of destination address. Each route has dst-address property, that specifies all destination addresses this route can be used for. If there are several routes that apply to a particular IP address, the most specific one (with largest netmask) is used. "

source: http://wiki.mikrotik.com/wiki/Manual:IP/Route

and the 10.10.1.254 device can ping lets say a 10.10.1.88 but the opposite doesnt work!
 
KBV
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 3:59 pm

In the case of Direct delivery routing mechanisms are not used. It uses ARP
Read about the Direct and Indirect delivery of IP :?
Last edited by KBV on Tue Jul 28, 2015 4:01 pm, edited 1 time in total.
 
Mashal
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 4:00 pm

BTW i was pinging the /30 device using mikrotik pinging tool via the connecting interface after its address was changed to /25
 
Ape
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Re: Subnet Routing problem!!!

Tue Jul 28, 2015 4:04 pm

Hi Mashal,

what you stated is right for routing in layer 3. But you have connected two overlapping networks to your router.
Without understanding subnetting and the internal working of the IP stack on a device, you won't be able to understand why your setup is not working and why
"By default forwarding decision is based only on the value of destination address. Each route has dst-address property, that specifies all destination addresses this route can be used for. If there are several routes that apply to a particular IP address, the most specific one (with largest netmask) is used. "
is not completely true in your case.

As KBV said:
In the case of Direct delivery routing mechanisms are not used. It uses ARP
Read about the Direct and Indirect delivery of IP :?
Please do the reading and try to understand the concept of subnetting. Afterwards you will be able to solve your problem by yourself :-)

Ape

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