Router interface questions

When you have a router with different interfaces - do you need to use them for specific things?

For example, when you say Wan - I assume you mean the internet. What is different about the configuration of a Wan and Lan? I was curious because some Routers have a Wan connection (which normally means a DSL connection or Cable connection on a commodity router/firewall). If you look at the Cisco Specs for 870 model series it has the following for the Wan Interface:

Cisco 871 10/100 Mbps Fast Ethernet
Cisco 875 Asymmetric DSL (ADSL)] over ISDN
Cisco 877 ADSL
Cisco 878 G.SHDSL

Does this mean I can't use the 871 router with a DSL connection?

Or not use the 877 as an internal router where I just want to route between subnets?

Or not use the 875 with normal ADSL unless it is over an ISDN line?

And what is G.SHDSL?

Thanks,

Tom

It's all down to what the manufacturer/designer were thinking of when they designed that box. Small units particularly tend to be targeted at the small office scenario where typically there will be a 'LAN' connected to a 'WAN' or possibly to the Internet, hence the labels on the ports. By contrast, on bigger devices you'll just see the ports labelled as Eth0, Eth1 etc because the potential applications are more varied. That's not to say that you can't use a small device for whatever you want - we use several little Draytek VPN routers here and a couple of ATI routers, all of which have 'WAN' and 'LAN' ports and they are miles from any WAN and deep within an enterprise network. If the interface physically works and the device will do what you want, then why not? Two things to bear in mind though - if you're using NAT or firewall facilities in the device beware of any design assumptions they've made that might trip you up ( www.firewall.cx/ftopict-3659.html ) and consider how reliable/resilient the thing will be

And I don't know what G.SHDSL is either

Hi All,

Shocked. No really I am. The Bishop not knowing what G.SHDSL is... especially as I am pretty sure he uses it for his WAN links

G.SHDSL = Synchronous Highspeed Digital Subscriber Line

It is the protocol used to supply an E1 (2Mbps) link to a business, and is sold as a data leased line service. (and is related to the same technologies as ADSL & VDSL)

G.SHDSL allows 2mb/s per copper pair, and can if required 'bond' pairs together to supply 2, 4, 6, or 8 Mbps links.

A typical scenario would have the corporate LAN connection to the cisco 878 via ethernet, and then the WAN port would be connected to a phoneline (copper pair) and configured for the G.SHDSL service.

Hope that helps

R

It helps me to know that there's still a lot I need to know...
Thanks Ranger!

so if you have say a 2501 cisco router that has 1 ethernet and 2 serial does that mean that any of the 3 could be lan or wan connections. so you could use the ethernet or one of the serial ports for wan ?