HP OfficeConnect 1620 Bonjour/mDNS

[StevenA89]

Hey all,

I have a small network with a HPE Office Connect 1620 and an ASA Firewall. We have multiple Vlans. I am trying to allow Bonjour/mDNS between two Vlans however when I have IGMP enabled on both the Firewall and the Switch I am not seeing the mDNS multicast IP being added into the Multicast Routing Table (224.0.0.251).

I am seeing others being added in. I am starting to think this is a switch limitation but have been unable to find any relating document to suggest this or otherwise.

Has anyone else had this issue?

Thank you,

Steven

[Emil_G · Accepted solution]

Hello, 

The Bonjour/mDNS multicast is not routable between subnets. See below resources.

Disclaimer

NOTE: One or more of the links above will take you outside the Hewlett Packard Enterprise Web site, Hewlett Packard Enterprise does not control and is not responsible for information outside of the Hewlett Packard Enterprise Web site

https://en.wikipedia.org/wiki/Multicast_address

Local subnetwork

Addresses in the range of 224.0.0.0 to 224.0.0.255 are individually assigned by IANA and designated for multicasting on the local subnetwork only. For example, the Routing Information Protocol (RIPv2) uses 224.0.0.9, Open Shortest Path First (OSPF) uses 224.0.0.5 and 224.0.0.6, and Multicast DNS uses 224.0.0.251. Routers must not forward these messages outside the subnet from which they originate

https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml

The range of addresses between 224.0.0.0 and 224.0.0.255, inclusive,
is reserved for the use of routing protocols and other low-level
topology discovery or maintenance protocols, such as gateway discovery
and group membership reporting.  Multicast routers should not forward
any multicast datagram with destination addresses in this range,
regardless of its TTL. 

That means that a normal multicast router should not forward Bonjour.

Various vendors are offering the feature called Bonjour gateway (or something similar) to resolve this limitation. Maybe you can check if the ASA Firewall supports Bonjour gateway or not.

[StevenA89]

Thank you  Emil_Gogushev

You saved me a lot of troubleshooting :).