Calnex SNE: What changed with VLAN Filters in version 6.1?

Please note: This article describes the VLAN Filter behaviour in versions 6.1 and 7.0 of the SNE software. The behaviour with regard to VLANs has changed in the Web UI (version 11.x onwards), and is described in a separate FAQ article.

In versions 6.1 and 7.0 of the SNE software, maps containing VLAN Filters behave slightly differently than in versions 6.0 and earlier.

The VLAN Filter works by telling other filters downstream of it on the “Passed” path of the VLAN filter to increase the offset from the start of the packet by 4 bytes when performing their pattern-testing. This additional offset allows for the additional 32 bits that the VLAN tag introduces. Other filters in the “Failed” path of the VLAN Filter should not have this additional 4-byte offset.

Prior to version 6.1 of the SNE software, other filters in the “Failed” path of the VLAN Filter DID have the additional 4-byte offset, which required a workaround that usually involved using duplicate filters to test for the different possible conditions. These workarounds are no longer required in SNE versions 6.1 and 7.0. Existing maps which did use such workarounds may no longer function as originally designed, and can be simplified to use a smaller quantity of filters.