vlan problem not pinging or all pinging

sonagccnasonagccna Posts: 44Member ■■□□□□□□□□
preparing for the ccna, and practiced with a simulator,in this
i have 11 pc's connected to switch 2950 and another 11 pcs connected to switch 1912.
in swicth 2950,

ip address=

fa0/1,2,3,4=vlan 1 (one)

fa0/5,6,7,8=vlan 2(two)

fa0/9,10,11,12=vlan 3(three); fa0/12 used for trunking, though i did not assign it to vlan 3 icon_eek.gif , it took it as vlan 3(?)

pc1-11 are assigned ip addresses thro

in switch 1912,

ip address=

e0/1-5=vlan 1(one)
e0/6-8=vlan 2(two)
e0/9-11=vlan 3(three)
and fa0/26 used for trunking

pc12-22 are assigned ip addresses thro


pc1 to pc 11 =OK

pc1 to pc17,21 =not pinging (sure as these 2 are in different vlans)

the problem is when i tried to
ping from

pc21 to pc1 =pings (though it is different vlan), why it is happening?
from all pcs connected to 1912 a ping to other pcs on 2950 whether they are in same vlan or different , the ping succeeds

similarly when i tried within the same switch 2950,
from pc1 to pc 6, it pings

it should not succeed right? as its in differnt vlan

i tried to debug,
show int f0/12 switchport, it displayed trunking encapsulation as dotq and while in 1912 as isl,
i thought this may be the cause.

but how to change the encapsulation?

plz someone clarify this


  • DrakonblaydeDrakonblayde Posts: 542Member
    If I remember right, 2950XL's don't support ISL, so you'd have to change the encapsulation on the 1912. Which sim is it, btw? If it's Network Visualizer, I'm not surprised, I stopped using it because it never did vlan's correctly for me.
    = Marcus Drakonblayde
    ==[X]===[X]====[ ]=====[ ]====[ ]==
  • tunerXtunerX Posts: 447Member ■■■□□□□□□□
    What kind of simulator are you using? Here is a little list:

    1900 ISL
    2900XL dot1q ISL
    2950 dot1q
    3500XL dot1q ISL
    3550 dot1q ISL

    The 1900 and the 2950 cannot trunk because they do not support the same encapsulation types. Not being able to trunk will not allow you to ping across VLANs. I think your simulator may be messed up. I have a 2950 and 1924. I will give your simulation a try.
  • netheadnethead Posts: 43Member ■■□□□□□□□□
    Yes, these two switches should not be able to trunk.

    Also the PCs should not all be able to ping themselves as the ports they are in are on different vlans. On the 2950 switch PCs 1-4 should be able to ping each other, PCs 5-8 should be able to ping each other and PCs 9-11 should be able to ping each other. No other pings should succeed as the ports are in different vlans, so I think this simulator has errors in it.

    I would suggest trying another simulator - hopefully someone will be able to recommend one (i've not used any simulators).
    "The time for talking is over. Now call it extreme if you like, but I propose we hit it hard, and we hit it fast, with a major, and I mean major, leaflet campaign. "
    - Rimmer, Polymorph
  • sonagccnasonagccna Posts: 44Member ■■□□□□□□□□
    thanks for all of your replies and suggestions!

    i'm using boson netsim5.27; may i expect questions with two 2950's in the ccna exam?

    what are all the other series of switches possible to be on ccna exam?
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