Why is it called a 'default' gateway?

If a host wants to send a packet to a host on a different network, it is sent to the default gateway. I would think that because it is called a default gateway, it is implied that there should be a choice of several, which is clearly not the case. Or could this situation ever be possible?

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Cisco Inferno

gateway is another word for a router. Unless you plan on having multiple routers/L3 switches in your network (which can exist), it is the function of your default gateway to take the packet from one network to another.

Params7

From what I know, its not really possible for a machine to have multiple gateways. Thus there is only one gateway, and it is always the default one lol.

I've learned not to question semantics on such a deep level in networking. Otherwise you come across things like Packet Internet Groper and Not-So-Stubby and you just keep on wondering.

Priston

How many gateways does this router have?
ip route 0.0.0.0 0.0.0.0 192.168.1.1
ip route 172.18.0.0 255.255.0.0 172.18.0.1

cisco_nerd

Params7 wrote: »

From what I know, its not really possible for a machine to have multiple gateways. Thus there is only one gateway, and it is always the default one lol.

I've learned not to question semantics on such a deep level in networking. Otherwise you come across things like Packet Internet Groper and Not-So-Stubby and you just keep on wondering.

It is actually quite possible for your machine/PC to have multiple gateways configured, as well as alternate IP addresses per interface. Also remember that your router running any routing protocol connecting to multiple networks will also have multiple gateways as a result.

The gateway/router is the device in your network that all your traffic will be addressed to should any address can not be found within the same subnet as the source (your PC will perform a logical AND to work this out). The default gateway/router is the device that will be a "catch all" scenario... i.e. in IOS you could issue the command ip-route 0.0.0.0 0.0.0.0 192.168.1 or under a DHCP pool default-router 192.168.1.1 to be a default route pointing all unknown addresses to the gateway 192.168.1.1 for it to work out how to get there based on its routing database (OSPF, RIP, EIGRP etc.)

Same concept that you see in Access Control List with the implied ip any any statement at the bottom of every list.

Hope this helps.

HP_Guy

Thanks for the responses folks. Yes I already appreciated how it applied to routers and just wondered if it was terminology that had drifted over to the PC-sphere. I find it interesting that @cisco_nerd says it is possible to have a PC configured with more than 1.

@Priston - 2

What do I win?

ajs1976

Run the route command from the command prompt on your windows pc to see how to add other routes to the routing table.

Edificer

In game of thrones, if Westoros wants to communicate with Winterfell, they need to use pigeons or send a human with a horse to deliver that message. Any messages that requires to go off-subnet (Westoros) need to hand over that packet to the pigeon or the messenger.

Deathmage

Edificer wrote: »

In game of thrones, if Westoros wants to communicate with Winterfell, they need to use pigeons or send a human with a horse to deliver that message. Any messages that requires to go off-subnet (Westoros) need to hand over that packet to the pigeon or the messenger.

you my friend win the default-gateway nerdiest response award. Made me laugh!!!

renacido

You probably have to be old like me to know this...

A gateway connects one network to another, which may or may not use the same network protocol. It's a TCP/IP world now but once upon a time you could have a network running TCP/IP, IPX/SPX (Novell), NetBIOS/NetBeui, DECnet, etc and so you have gateways for each of these that routed traffic for that protocol from one network to another OR to encapsulate packets from one network and transport them via another using a different protocol. So a machine on a Novell network used IPX/SPX for internal routing but used TCP/IP to route messages to/from the Internet, "IP over IPX".

Or that's the gist of it anyway, it's been 20 years or so since I've worked on a network that wasn't pure native TCP/IP.

theodoxa

Params7 wrote: »

From what I know, its not really possible for a machine to have multiple gateways. Thus there is only one gateway, and it is always the default one lol.

route add <NETWORK> mask <SUBNET MASK> <NEXT HOP> metric 1 -p

You can add static routes to a Windows PC from an Elevated (Start, Type cmd, Right Click cmd.exe and select Run as Administrator) Command Prompt using the above command. Having multiple gateways (static routes) is useful if you have a lab, but your home router doesn't allow you to configure static routes on it. For example, I have an ASA at the edge of my lab. I add a static route on my PC to the Subnet(s) used in my lab with the ASA as the Next Hop or Gateway. Traffic destined for the lab gets sent directly to the ASA, bypassing my router, whereas any other traffic (except traffic destined for the same subnet as the PC) gets sent to the router and out to the internet.

powmia

Edificer wrote: »

In game of thrones, if Westoros wants to communicate with Winterfell, they need to use pigeons or send a human with a horse to deliver that message. Any messages that requires to go off-subnet (Westoros) need to hand over that packet to the pigeon or the messenger.

This doesn't answer the OP's question. How does Ramsay know to which pigeon to ARP for, and what is the significance of a default pigeon? Surely he could just hand a message to a person on a horse, but that person may only know how to get to the wall.