subnetmasks for gateways

Ok, I am going to clarify this exact question as stated in the above.

In this case, as the question is stated, the Next_Hop_Address is on the remote end of a directly connected interface. The IP address for that next hop (192.168.2.1) is on a common subnet as the router's interface which connects to that next hop address. Therefore, a mask is not required because the router can what the mask is due to the fact that the router itself has an ip address on that (same) interface, and part of the ip address configuration on that (same) interface includes the subnet mask.

HOST----------------ROUTER-*------------------*-ROUTER--------------*-HOST whatever 192.168.2.x/y

192.168.2.1/y 172.16.3.x

If you can't follow this, please ask again ----- but nicely.

My sincere apolgoy if I have offended you.

Doan

oh, that's very nice of you. are you still mad at me because I made you eat the crow once? I appreciate when people try to help me, because I do the same. What I do not appreciate is when people try to help my by offering their routers to me instead of a simple answer, or when people do not read my question carefully and start misinterpreting it and finally calling me an idiot. You call these people well-seasoned? They have no f****ng clue about static routing and they pretend to be smart asses? Well, what would you expect in return if you will call someone idiot? In your case, you are a total moron, because you are calling me a troll.

The Dude

You misunderstood the context in which I was referring to a 'door'. I meant when a host wants to get out of its subnet it needs a door. That 'door' (or gateway) is the way out. That's pretty simple to follow right?

So this gateway must be close if the host is going to use it. By 'close' I mean the host doesn't have to go through any other doors to get to it. On the other side of the door is a new place ... a new subnet. Look at it this way ...

PC (net A) -- door A -- (net B) -- door B -- (net C)

So each 'door' or router has an interface in the previous network and in the next subnet. Follow that?

Let's go back to you original question ...

In routing terms you're incorrectly referring to "192.168.2.1" as a 'gateway' when it's actually a 'next hop'.

Either way it doesn't matter because the principle is the same ...

1) For the PC, 'door A' is a gateway (out of the subnet) and because door A has an interface in the PC's subnet (so the PC doesn't have to go through any other doors to get to it ... exclude the PC's own interface as it's implied that's the way out of the PC) and the PC knows what the subnet mask is for its own subnet so you don't have to tell it what the mask is for 'door A' ... because it's in the same subnet on the PC's side. 2) You can call 'door B' a "gateway" if you like. It's a gateway for 'door A' to get to 'net C' and because 'door B' has an interface in the same subnet as 'doorA' and 'door A' knows the subnet mask for that subnet you don't have to tell it what subnet mask 'door B' is using.

Understand?

BernieM

PC (net A) -- door A -- (net B) -- door B -- (net C)

'door A' is the PC's "gateway". 'door A' refers to 'door B' as the "next hop" for traffic going to 'net C'

The PC doesn't refer to a 'next hop' .. it only knows of a 'gateway' and because the gatways interface is in the

Where did you get not so bright idea from?

"Gateway" has a very particular meaning in a networking, and believe me, it is NOT the next hop address specified in a static route!

Aubrey

Again where did you get this next hop address is a "gateway" rubbish???

No where in the Academy Program curriculum does it call the next hop ip address in a static route a "gateway"!

Please do yourself a massive favour and stop referring to it as one. I can assure you that once you do that this massive non-existent problem you've invented about the requirement or non-requirement for a subnet mask will just disappear.

Aubrey

Really? I thought you were one of the good ones in this newsgroup ... Well, are you calling cisco rubish or are you calling me a liar?

Please do yourself a massive favour and stop calling me a liar. I do not care if you call cisco "rubish"

I can > assure you that once you do that this massive non-existent problem you've

Since you are so sure, I will make you eat crow too!! Go to: CCNA 2 - 6.1.2 - click figure 3 on the left - Check the bottom and read carefully what is specified as a gateway.

And then, there is this e-lab on the right where I got the question from. By the way, I already found the answer myself, because I noticed that whoever replied jumped to conclusions that are totally irrelevant to my question.

One more thing: It looks like all of you that replied to my post so far, have a common problem:

You seem all to confuse the word "way" with the word "away", therefore, the word "gateway" with the word "gateaway". "Gateway" is not to just get out of your/your neighbour' sub/network, but also to get into your/your neighbour' sub/network;

The Dude

PS: I want all you to apologize to me for calling me idiot, stupid, troll, liar and so on. If you don't I payed you back in the same coin.

Really?

That was a very generous offer, and instead of saying 'no thanks,' you harshed all over the guy who was just trying to assist.

I seem to recall it is you who have started the "dunce / moron / idiot" name calling.

Yes.

The responses I saw to your question were pretty accurate. It seems that you are having a hard time with them because they clash with some (incorrect) pre-conceptions you have developed.

I may be a total moron, but not for that reason, nor for any lack of understanding about the subjects brought up within this newsgroup.

Have a nice day. And good luck with your studies.

You just don't know you stuff.

Well, I guess, it is the level, In your terminology you call a far end iBGP peer a gateway because we call this a next-hop?

What about iBGP neighbors? Are they next door or next hop ? Hahahaha....

And I was not offering you routers. I *suggested* to buy one yourself. That is something different. It seems to me that you still not recovered from your frustration?

That is correct. After my *suggestion* I was called "you moron" by this gentleman who calls himself "The Dude". Wrong name....

Yes, you are. Go back to your CCNA books and read carefully.

The Dude wrote in alt.certification.cisco:

Because the router 1 will know the subnet mask. When the interface on router 1 was configured you need to give ip address and subnet mask. Since the router 2 IP (192.168.2.1) is on the same subnet there is no need for specifying the subnet mask.

As I said in an earlier post, I got the answer, but thanks anyway, although your answer is not complete.

I repeated myself so many times about dealing with 3 sub/networks in this scenario, but they all flamed on me until I had to refer them to the cisco academy to do some studying. Now everyone seems to have shut up.

Here is an explaination for you smart alecky people that have not apologized yet:

There are two ways of specifying the static IP route for the packets to go from the network behind R 1, (I will call it net1) to the network behind R 2 (I will call it net 2), where R1 and R 2 are connected directly:

1. Enter the IP address and subnet mask of net 2 (destined network) and serial interface of R1 ( gateway ) (i.e. s0)
2. Enter the IP address and subnet mask of net 2 (destined network) and the ip address of the next hop (gateway), which is the serial interface of R 2

And, please, do not forget that the gateway can be anywhere in the network, and can serve for both, letting traffic in or out.

Now, let's get back to business:

My question " why don't we put subnetmasks for gateways " is clearly related to the second scenario, where the subnet mask of the next hop (gateway), which is the serial interface of R 2, is different from the subnet mask of both, net 1 and net 2.

The Dude

The Dude wrote in alt.certification.cisco:

I don't see how?

And I noticed this just now, as this is probably the source of most confusion in this thread, what you are saying is not correct.

Lab asks you to forward all traffic destined for 172.16.3.0/24 to nex hop router 192.168.2.1 so the router 1 in this scenario doesn't have

172.16.3.0/24 connected to it at all.

Traffic from next hop router (192.168.2.1) for 172.16.3.0/24 is not going to router 1, it is some network directly connected to it or he is forwarding traffic destined for 172.16.3.0/24 to some other router.

192.168.2.1 cannot be a gateway for 172.16.3.0/24 as a gateway for that network is some ip addres in that network on some (other) router.

192.168.2.1 can only be called a next hop router in this scenario and not a gateway as is't not forwarding traffic for 172.16.3.0/24, it is forwarding traffic destined for it!

The Dude wrote in alt.certification.cisco:

No they aren't.

Lets say that the source network is 192.168.16.0/24

No, the gateway for the 192.168.16.0/24 network is in that subnet! Probably 192.168.16.1/24. If you put 192.168.2.1/24 as a gateway for the hosts in the 192.168.16.0/24 network, it won't work as the host don't know where is 192.168.2.1/24.

Subnetwork A (192.168.16.0/24) has its own gateway in that same subnet A, 192.168.16.1/24.

Hosts in 192.168.16.0/24 don't know anything about 192.168.2.1, their gateway for the outside world is 192.168.16.1/24.

I see what's going on here. You are confusing a few concepts. In your ip route statement, you are really saying this

If you want to get to 172.16.3.1 through 172.16.3.255, then use

192.168.2.1 as your next hop address. The 255.255.255.0 tells the router what addresses you need to worry about. The last 0 tells the router "don't worry about the last octet, if the first three are 172.16.3, then send it to 192.168.2.1"

*IF* this is the *only* way out of your network, then yes, it can qualify as your default gateway. But it doesn't have to be *the* gateway. After all, this static route is a just a direction on how you can get to 172.16.3.0/24 network.

You don't need a "subnetmask" for your gateway address because you don't need to worry about which part of the 192.168.2.1 is important. When the router needs to send a packet via the next hop of 192.168.2.1, the router will look up how to get to 192.168.2.1. Typically, it will be directly connected so the router will just check the arp cache and change the Ethernet header and send the frame on its merry way. If it does *NOT* know how to get to 192.168.2.1, then it will go back to the routing table and look up which next-hop address it should use for

192.168.2.1. This is called recursive lookup.

I typed it exactly as it was on the cisco lab, and I added my comment: "The way the sentence is built, it took me a while to understand" From what you write, you do not seem to get it yet. The next hop is considered a gateway because via that hop the packets go to the destined network ....

I am not dealing with this anymore... life is short!

The Dude

good