Stub Router

Folks;
I am having a hard time understanding a Stub Router topology. On the provided link
Google Image Result for http://www.cisco.com/en/US/i/100001-200000/130001-140000/135001-136000/135835.jpg

is the stub router the center router with multipule connections or are the six routers at the bottme called stub routers?

thank you

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Comments

Forsaken_GA

stub routers generally only have one egress path, that's why they're stubs.

With that in mind, the router at the top in the link can't possibly be a stub, it has multiple egress paths (it is in fact, a hub router)

And then there's the fact that the text you linked very clearly states the following:

A stub router can be thought of as a spoke router in a hub-and-spoke network topology

networker050184

The six at the bottom are the stubs. Think of the stub as router with a single connection back to the hub.

Damn you're quick!

ColbyG

networker050184 wrote: »

The six at the bottom are the stubs. Think of the stub as router with a single connection back to the hub.

Damn you're quick!

Looks like only four are stubs.

CiskHo

Per Wiki: A Stub router, One-armed router or router on a stick is a router that routes traffic between virtual local area networks (VLANs). It has only a single Ethernet NIC that is part of two or more Virtual LANs, enabling them to be joined.

*edit* Seems like Wiki's definition may be flawed. Surely a stub router doesn't require an ethernet connection.. unless a "stub router" is required to be connected to a switch. I dunno...

networker050184

ColbyG wrote: »

Looks like only four are stubs.

Ha, I only looked at the image preview and didn't see that link. Attention to detail!

Forsaken_GA

ColbyG wrote: »

Looks like only four are stubs.

yeah, the last two having a link between them is kind of funky and makes no sense in the context of the actual article

networker050184

CiskHo wrote: »

Per Wiki: A Stub router, One-armed router or router on a stick is a router that routes traffic between virtual local area networks (VLANs). It has only a single Ethernet NIC that is part of two or more Virtual LANs, enabling them to be joined.

I would think that IF any of those routers was a stub router then it would be the one at the top. However, I don't think any of those are common stub routers as I don't see any VLAN info. I'd could use some clarification as well. I tihnk point to multipoint when I see that topolgy but I was never any good in that area.

A stub router has nothing to do with whether it has VLANs or not. Wikipedia isn't always the best source of information.

e24ohm

Forsaken_GA wrote: »

stub routers generally only have one egress path, that's why they're stubs.

With that in mind, the router at the top in the link can't possibly be a stub, it has multiple egress paths (it is in fact, a hub router)

And then there's the fact that the text you linked very clearly states the following:

A stub router can be thought of as a spoke router in a hub-and-spoke network topology

i might be confusing myself...what if the router at the top had each of the 6 links configured on a Virtual Interface?

Forsaken_GA

CiskHo wrote: »

I would think that IF any of those routers was a stub router then it would be the one at the top. However, I don't think any of those are common stub routers as I don't see any VLAN info. I'd could use some clarification as well. I tihnk point to multipoint when I see that topolgy but I was never any good in that area.

#1 Do not use wikipedia as a reliabe resource for network documentation. It will come back to hurt you

#2 'stub' is one of those unfortunate network terms that has multiple meanings, and depends entirely on the context it's being used in. The wiki definition is not entirely incorrect, it's just not absolute, as a stub router has an entirely different meaning from that when it comes to ODR, EIGRP, and OSPF

Forsaken_GA

e24ohm wrote: »

i might be confusing myself...what if the router at the top had each of the 6 links configured on a Virtual Interface?

Doesn't matter, it connects to 6 different routers. Even if it is a multipoint configuration, it's not a stub router (at least, not in the context of the article that contains the image), it's a hub router.

e24ohm

Forsaken_GA wrote: »

#1 Do not use wikipedia as a reliabe resource for network documentation. It will come back to hurt you

#2 'stub' is one of those unfortunately network terms that has multiple meanings, and depends entirely on the context it's being used in. The wiki definition is not entirely incorrect, it's just not absolute, as a stub router has an entirely different meaning from that when it comes to ODR, EIGRP, and OSPF

I was having problems with Stub Routers on page 95 - 96 of CCNP BSCI Official Exam Certification Guide 4th edition, by B. Stewart.

On page 96: "The stub router has only one neighbor, a distrubtion layer router. The remote router only needs a default route pointing to the distributino router - everywhere else can be reache via that router.

However, after what everyone has typed, I beleive i understand now...thanks

Figure 4-1 - The distribution router would be Router A right?

Forsaken_GA

i don't have the book, so I can't say for sure, but generally speaking, if you only have one egress link, and you can reach any destination outside of your network via a default route pointing to that link, it's a stub router. How a stub router operates has different meanings depending on the type of routing environment (ie, in OSPF, a stub network propagates LSA's and routers differently than a non-stub network, in EIGRP, whether or not a router is a stub router effects the query range, etc)

But again, it's a fairly nebulous term. You could describe virtually all residential internet connections as stub networks as well, even though they usually aren't participating in any kind of routing at all.