general VLAN trunk question

phatsoundz

this may be a rhetorical question but i gotta ask, i'm having trouble locating the answer in my books, and i fear that i have another poor practice exam question i came across online;

if there's a partial mesh topology of switches all running various trunks, vlans, if one trunk goes down, do they all go down? or just that trunk/vlan will be unreachable?
-the answer is that all vlans are unreachable

-am i missing something? is this right?

rjbarlow

If a trunk fails only the breaked segment of the network become unreachable, if there are reduntant links/paths they replace failed links, normally.

dtlokee

phatsoundz wrote:

if there's a partial mesh topology of switches all running various trunks, vlans, if one trunk goes down, do they all go down? or just that trunk/vlan will be unreachable?
-the answer is that all vlans are unreachable

There are too many variables to answer this based on the information provided. When you say a "partial mesh" that would indicate there may be devices with only a single connection to a switch, and if one of those devices is the "router on a stick" providing inter-vlan routing then yes all of the VLANs will be unreachable. If the active trunk between two switches fails it could take up to 50 seconds for another trunk to transition to forwarding (20 for maxage + 15 listening + 15 learing) so again it is possible during that period that all VLANs would be unreachable. To reduce the forwarding delay, you can use the Cisco extensions to 802.1d spanning tree such as portfast, uplinkfast, backbonefast, or enable 802.1w rapid spanning tree (PVRST) and configure your edge ports with "spanning-tree portfast" and from global config I would use "spanning-tree portfast bpdufiler default" just in case a bpdu is received on an interface, tht interface will lose it's portfast status and become a regular spanning-tree port again.

HTH

kir

how does one easily pass tha ccna exam

Netstudent

uhhhhh...Thats a really "off this topic" type of question. There is no easy route, unless you are a cheater. Who cares about how easy or hard it is. It's not about that. It's not about seeing how easy you can get by, it's about seeing how well you can do and how well you can gain the knowledge. Nothing comes easy in the IT industry unless you want to work helpdesk for the rest of your life. A lot of people work very hard and take this very seriously on this forum, so asking a question like that isn't your best "first post".

Anyways good luck.

blackmage439

If you could post the full question on here, we might be able to help you a lot better. A "partial mesh of switches" could mean anything.

But I think the underlying concept of the question is that if the switches were arranged in such a fashion that one switch was the central hub of all communication, a failure on that would cause the network to collapse.

mikej412

kir wrote:

how does one easily pass tha ccna exam

One studies really really hard until they have learned all the topics mentioned in the CCNA Exam Blueprint

Netstudent wrote:

There is no easy route, unless you are a cheater.

If someone is looking to "****" their way to the CCNA, I usually suggest they just buy a fake MBA (or make their own) since they can make more money with a fake MBA than a fake CCNA (plus I'll work for an idiot if it pays well, I just don't want to have to work with idiots ).

tech-airman

phatsoundz wrote:

this may be a rhetorical question but i gotta ask, i'm having trouble locating the answer in my books, and i fear that i have another poor practice exam question i came across online;

if there's a partial mesh topology of switches all running various trunks, vlans, if one trunk goes down, do they all go down? or just that trunk/vlan will be unreachable?
-the answer is that all vlans are unreachable

-am i missing something? is this right?

phatsoundz,

Did the question mention that there was a router involved to route between the VLANs?

phatsoundz

tech-airman wrote:

phatsoundz wrote:

this may be a rhetorical question but i gotta ask, i'm having trouble locating the answer in my books, and i fear that i have another poor practice exam question i came across online;

if there's a partial mesh topology of switches all running various trunks, vlans, if one trunk goes down, do they all go down? or just that trunk/vlan will be unreachable?
-the answer is that all vlans are unreachable

-am i missing something? is this right?

phatsoundz,

Did the question mention that there was a router involved to route between the VLANs?

no sir, just switches...i know its a bit general, but this is what it is.