InterVLAN: ISL and 802.1q Trunking

[worldcalltel]

Hi,

I have a 2948G-L3 connected to 3524XL via 4 Fast Ethernet Interface using port-channel ISL trunk. I want to expand my LAN, so I have a 3508G connected to 3524XL thru 2 Gigabit Ethernet Interface. From 3508G, the remaining Gigabit Ports are connected to 2948G-L2. My question is, the 2948G-L2 only supports 802.1q and all the interconnection of my switches is ISL. 2948G-L3 <---ISL---> 3524XL <---ISL---> 3508. Since I want to expand my LAN, I purchased 2948G-L2. If I connect my 2948G-L2 to 3508 via 802.1q, would it be possible if the PC connected to 2948G-L2 can access the server connected to 3524XL?

Diagram:

---------------

| 2948G-L3 |

---------------

| | | |

| | | | ISL

-------------------

| 3524XL |--Server

-------------------

| |

GigabitEth | |

ISL | |

-------------------

| 3508G |

-------------------

|

| 802.1q

|

-------------------

| 2948G-L2 CatOS |

-------------------

|

|

PC

Server IP Address VLAN20: 10.10.10.1

PC IP Address VLAN20: 10.10.10.26

[Thotsaphon Lueangwattanaphong · Accepted solution]

hi Jaime,

As long as you correctly configure both switches to form a trunk then it should be fine.

ISL doesn't have the native vlan concept. It will encapsulate all packets and decapsulate at the other end.

To answer your question. Yes, PCs can access servers.

HTH

Toshi

[Jon Marshall]

Jamie

Just to add to Toshi's post. Trunks, whether they are ISL or 802.1q are only significant on the local trunk link so you could if you wanted connect your switches

sw1 -> ISL -> sw2 -> 802.1q -> sw3 -> ISL -> sw4 -> 802.1q -> sw5

Each switch in the path will do the "right" thing in terms of encapsulation/deencapsualation (ISL), tagging/untagging 802.1q.

Jon