How many ports can one 1841 support?

[yytellmey]

Hi,

I have a Cisco 1841 router. There are two fixed FastEther interfaces and two slots.

I am going to add two 4-port EtherSwitch HWIC cards into these slots. Can I get four router interfaces when I added these two cards into the router? That is two built-in interfaces and two interfaces on two cards, totaly four interfaces.

My concern is that I read a sentence from Cisco website for 1841 "When two HWICs are installed in the same chassis, they have to be physically stacked together." Does it mean even though I add two cards into the slots, I get only one more router interfaces, totaly three interfaces. So a 1841 can support max three router interfaces, right?

Thanks,

Justin

[Danilo Dy]

If you stack two 4-port EtherSwitch HWIC cards, you connect one of their 4 port together with a crossover cable, therefore you left with 6 EtherSwitch ports. Intra-chassis stacking allows all the Fast Ethernet interfaces on the two HWICs to participate in the same Layer 2 domain.

You can trunk these two 4-port EtherSwitch HWIC using an external Ethernet cable to one of the router fixed port, leaving you with 5 EtherSwitch port and one fixed L3 port.

[yytellmey]

Hi Danilo,

If I don't stack the two HWIC cards, can I get 4 L4 ports? That is 2 built-in L3 ports on the router, and 2 ports on the 2 HWIC cards (1 L3 port on each HWIC card). Totally, can I get 4 L3 ports?

Thanks,

Justin

[Danilo Dy · Accepted solution]

Hi Justin,

I can't try your scenario to prove it, what I see in the doc is;

1. EtherSwitch port is not a L3 port its a L2 switching port. However, you can configure interVLAN routing

2. No more than two Ethernet Switch HWICs or network modules may be installed in a host router. Multiple Ethernet Switch HWICs or network modules installed in a host router will not act independently of each other. They must be stacked, as they will not work at all otherwise. Two 4-port EtherSWitch HWIC has to be stack using an external crossover cable utilizing one port for each card. This applies to your situation.

Look at the discussion below, they can configure routing directly in the EtherSWitch port using a certain IOS release http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=WAN%2C%20Routing%20and%20Switching&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.1ddd300c

Here's the link on how to configure EtherSwitch HWIC http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00802c6bb6.html

[yytellmey]

Thanks a lot, Medan.

Justin