Network topology ( the combination of access and trunk)

[lucky_67012001]

Hello network engineers,

I am new to networking and just finished the access and trunk chapter.

I decided to start a new lab, one which looks like this:

Switch3560nr1---switch3560n2--switch3560nr3-switch3560nr4

On switch 3560nr1 i have configured the following:

chose a random vlan for management(vlan 225), i created an access uplink port ( in vlan 225),

On switch3560n2( the downlink to Switch3560nr1  is also in access in vlan 474),the uplink to Switch3560nr3 is configured as trunk)

Switch3560nr3 downlink to switch3560nr2 is configured as trunk too and the uplink to switch3560nr4 is configured in trunk.

My goal is to make switch3560nr1 to reach switch3560nr4 by ping, the only way i managed to do that is by configuring switch3560nr2 and switch3560nr3 ( in trunk native vlan 225) below you can see the configuration for each switch:

switch3560nr1:

interface GigabitEthernet0/1

switchport access vlan 225

switchport mode access

!

interface GigabitEthernet0/2

!

interface Vlan1

no ip address

shutdown

!

interface Vlan225

mac-address 00e0.8fbc.c601

ip address 172.16.1.1 255.255.255.0

switch3560nr2:

interface GigabitEthernet0/1

switchport access vlan 474

switchport mode access

!

interface GigabitEthernet0/2

switchport trunk native vlan 225

switchport trunk encapsulation dot1q

switchport mode trunk

switch3560nr3:

interface GigabitEthernet0/1

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface GigabitEthernet0/2

switchport trunk native vlan 225

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface Vlan1

no ip address

shutdown

switch3560nr4:

interface GigabitEthernet0/1

switchport trunk encapsulation dot1q

switchport mode trunk

!

interface GigabitEthernet0/2

!

interface Vlan1

no ip address

shutdown

!

interface Vlan474

mac-address 0040.0bb0.7a01

ip address 172.16.1.2 255.255.255.0

switch3560nr4#ping 172.16.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/0 ms

Is there any other way that i can make switchNR1 each switchNR2 by ping, withaut adding the native configuration ?

[Martin L]

usually Pings stay within same vlan. you need routing enabled if u want to ping vlanx to vlanz. your setup will not work for other interface vlan y pings but goal of trunks is to move various vlans traffic.
you should use trunks on all links between switches (real world).

this site is more technical support rather then technology learning support, u should go to CLN -lots of topics in ccna group about trunks, access links
https://learningnetwork.cisco.com/groups/ccent-ccna-routing-switching-study-group

[Giuseppe Larosa]

Hello Lucky,

you have joined two different broadcast domains Vlan 225 and Vlan 474.

This is not considered best practice in real world.

Your question is appropriate you make the end to end connectivity to happens thanks to the native setting on the trunk port of second switch.

In real world you would have configured Vlan 225 in all switches and you would have configured an appropriate SVI interface Vlan 225 on each of them including switch4.

In this scenario the native Vlan setting could be different and each Vlan would stay separate with no join of Vlan 225 and Vlan 474. Just Vlan 225 would need to be permitted in all trunk ports both sides of each link.

Your lab demonstrates the capability of native Vlan to provide backward compatibility for untagged traffic and with different settings at the two ends of the chain of switches  you actually join broadcast domains Vlan 225 and Vlan474.

Because switch4 SVI is Vlan 474 and not Vlan225 but ping works.

This is a trick that sometimes is used when there is a specific need to join two different Vlans. It is not common practice.

As noted by other colleague this is not an example of inter Vlan routing it is a trick to join two vlans.

Hope to help

Giuseppe

[Martin L]

in other words, he got lucky  :)