Difference between WAN & LAN ports on 800 routers

[Network Digger]

Hi there,

i was checking the cisco 800 routers data sheet, found it says it has 4 LAN 09port and 1 WAN port, all ethernet interfaces. 

My question is, is there a difference between these ports? As i remember port 0 is the WAN port and port 1 till 4 are the LAN ports, why can’t I use port 1 for the WAN connection? Are there a certain configuration or commands supported on the WAN ports that are not supported on the LAN ports?

thanks in advance. 

[Deepak Kumar]

Hi,

You didn't share complete model number but I am taking a "Cisco 892FSP" router for the reference. As this router is having "1-port GE or 1‑port SFP, 1-port GE" (2 ports) as WAN and 8 Ports for LAN (Managed Switch). As 8 ports are layer 2 ports and it is working as Switchport. So those ports we can't use as WAN because we will face issue NATing, FIrewall configuration as. 

https://www.cisco.com/c/en/us/products/collateral/routers/800-series-routers/data_sheet_c78-519930.html

[paul driver · Accepted solution]

Hello
On a device like this usually you would have switchports (in your case -4 LAN) and routed ports (WAN port)

Switchports are layer 2 specific meaning that can belong to a vlan in an access mode or to many vlans in a trunk mode But because of there L2 capability they cannot support any form of routing (l3 - ip addressing , belonging to a routing protocol).

Switchports support various L2 protocols such like PPP, Frame relay, LLDP CDP, VTP,STP etc..as such they usually cannot become routed ports however In higher end switches switchports can become routed ports by turning of switching mode (no switchport)

Routed ports like your WAN port support l3 protocols (ip addressing, rip/opsf eigp bgp, pim etc..).and as such do not support the protocols that a switchport can at L2.

So you would use your wan port to connect to the ISP or another L3 routing device and the LAN ports to your end hosts or another switch via a trunk or access port to extend your l2 capability

[mlevi]

Hello.
I understand this is old thread but I couldn't find any other piece of information regarding motivation behind WAN ports.
They seem to me to be more limited than combination of L2 switchport and virtual VLAN interface. I'm facing situation where ISP requires me to run PPPoE on trunk interface on vlan 21. This is quite typical with home offers where multiple services are delivered (internet, phone, TV). Does this mean that router's WAN interface can't be used in this scenario ?

What can be done on WAN port and can't be achieved with switchport + vlan interface ?

[Joseph W. Doherty]

"What can be done on WAN port and can't be achieved with switchport + vlan interface?"

Depends on device.  On Cisco's Enterprise grade switches, switch ports and routed ports are just two different sides of the same coin, but which you select impacts configuration options and default operations of the port.

On low-end "routers" like an 8xx, switchports and WAN ports often have very different feature options, which I suspect, are tied to the hardware (which likely keeps costs down, i.e. some hardware only supports typical LAN port needs, while some of the hardware only supports WAN port needs).

Typically the WAN port, on these "routers" can support additional features such as QoS, NAT, etc., which the LAN ports cannot.  Conversely, such device LAN ports might support STP, PoE, etc., which the WAN port cannot.