1. Home
  2. Cisco Systems
  3. router not reachable over a trunk link

router not reachable over a trunk link

Hi there, I have this situation:

my pc is connected to a port of a C2950G-EI switch that is assigned to VLan77

the above C2950G switch is connected to a C3508 switch. I configured both ports involved in this connection as trunk link 802.1q.

the C3508 switch is connected to a C2950T switch. I configured both ports involved in this connection as trunk link 802.1q.

a 1721 router is connected to a port of the above C2950T switch. That port is configured as trunk link 802.1q.

I can't ping the router from my pc. Why? Trunk links aren't supposed to let me ping the router easily? Do I have to configure something on the router also? But I can't see anything regarding vlans and things like that, on the ethernet interface of the router.

Where is my mistake?

Thanks in advance.

blu_aqua

P.s.: here is a wonderful :-) example of ascii art that "should" help you get a quick glance on my situation. The "t" simbolizes a trunk link.

[MyPC]-vlan77>[C2950G][C3508][C2950T][router1721]
Reply to
blu_aqua
Loading thread data ...

ok.. let me elabroate your topology:

/[2950G][3508][2950T] pc/ ^ | [1721]

Problem: Your pc cannot ping the router?

////////// Ok, let to clarify a few things here

How many Vlans do you have? Can your pc ping its default gateway? Can your router ping the other switches? Can your pc ping the other switches? Did you create some sort of sub-interface on the router?

Cheers, CC

Reply to
cc

Thanks for your answer! :-) It's not clear from your ascii art (nor from mine). Let me state it: the router is connected to the 2950T [2950G][3508][2950T] pc/ ^ | [1721]

About your questions:

I have 6 vlans.

pc default gateway is supposed to be the router itself. Can I do that? Or am I wrong? If I'm wrong: who should be the default gateway? the ip address of the vlan? Do I need a different gateway for each vlan? Please give some IOS command examples :-)

Yes

No because the other switches are on VLAN1 (management vlan). But my pc can ping other pc in VLAN77 (77 is the vlan of my pc)

No. Should I? I currently have ATM0, ATM0.1, Fastethernet0. Consider that I'm going to put a pix 506e between the router and the LAN....so maybe I should create some sub-interface on that. If possible please provide some IOS command examples.

"cc" ha scritto nel messaggio news: snipped-for-privacy@z14g2000cwz.googlegroups.com...

Reply to
blu_aqua

To troubleshoot Trunking you need to check on a few things : Make sure the Layer2 int mode configured on both ends of the link are valid. Should be either trunk,dynamic or nonegotiate. Is the native vlan the same on both ends of the trunk?

Is the mask/address range the same on PC and router?

Cheers, DB

Reply to
DB

"DB" ha scritto nel messaggio news: snipped-for-privacy@f14g2000cwb.googlegroups.com...

It's "trunk" on both sides

yes (why does this matter?)

yes

Reply to
blu_aqua

Native VLAN should be the same otherwise spanning-tree loops might occur. Speaking of STP, did you check the STP on the switches.Are they the same?

Reply to
DB

U¿ytkownik "blu_aqua" napisa³ w wiadomo¶ci news:4yu4e.38760$ snipped-for-privacy@tornado.fastwebnet.it...

Yes, you should create subinterface for each VLAN, that you want to comunicate with router (or between VLAN). For each subinterface you must configure encapsulation and vlan-number identifies the VLAN for which the subinterface will carry traffic.

cheers,

Kamil Olszewski

Reply to
Kamil Olszewski

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.