Cisco Cisco Expressway Maintenance Manual
4.
Configure the DNS zone settings as follows:
Field
Guidelines
Hop
count
count
When dialing by URI via DNS, the hop count used is that configured for the DNS zone associated
with the search rule that matches the URI address (if this is lower than the hop count currently
assigned to the call).
with the search rule that matches the URI address (if this is lower than the hop count currently
assigned to the call).
If URI address isn't matched to a DNS zone, the query may be forwarded to a neighbor. In this
case, the hop count used will be that configured for the neighbor zone (if this is lower than the
hop count currently assigned to the call).
case, the hop count used will be that configured for the neighbor zone (if this is lower than the
hop count currently assigned to the call).
H.323
and SIP
modes
The H.323 and SIP sections allow you to filter calls to systems and endpoints located via this
zone, based on whether the call is located using SIP or H.323 SRV lookups.
zone, based on whether the call is located using SIP or H.323 SRV lookups.
Include
address
record
address
record
This setting determines whether, if no NAPTR (SIP) or SRV (SIP and H.323) records have been
found for the dialed alias via this zone, the Expressway will then query for A and AAAA DNS
records before moving on to query lower priority zones.
found for the dialed alias via this zone, the Expressway will then query for A and AAAA DNS
records before moving on to query lower priority zones.
You are recommended to use the default setting of Off, meaning that the Expressway will not
query for A and AAAA records, and instead will continue with the search, querying the remaining
lower priority zones. This is because, unlike for NAPTR and SRV records, there is no guarantee
that the A/AAAA records will point to a system capable of processing the relevant SIP or H.323
messages (LRQs, Setups, etc.) - the system may instead be a web server that processes http
messages, or a mail server that processes mail messages. If this setting is On, when a system is
found using A/AAAA lookup, the Expressway will send the signaling to that destination and will
not continue the search process. If the system does not support SIP or H.323, the call will fail.
query for A and AAAA records, and instead will continue with the search, querying the remaining
lower priority zones. This is because, unlike for NAPTR and SRV records, there is no guarantee
that the A/AAAA records will point to a system capable of processing the relevant SIP or H.323
messages (LRQs, Setups, etc.) - the system may instead be a web server that processes http
messages, or a mail server that processes mail messages. If this setting is On, when a system is
found using A/AAAA lookup, the Expressway will send the signaling to that destination and will
not continue the search process. If the system does not support SIP or H.323, the call will fail.
Zone
profile
profile
For most deployments, this option should be left as Default.
5.
Click Create zone.
Configuring search rules for DNS zones
If you want your local Expressway to use DNS to locate endpoints outside your network, you must:
■
■
create a DNS zone and set up associated search rules that use the Pattern string and Pattern type fields to
define the aliases that will trigger a DNS query
define the aliases that will trigger a DNS query
For example, rules with:
■
a Pattern string of .*@.* and a Pattern type of Regex will query DNS for all aliases in the form of typical URI
addresses
addresses
■
a Pattern string of (?!.*@example.com$).* and a Pattern type of Regex will query DNS for all aliases in the
form of typical URI addresses except those for the domain example.com
form of typical URI addresses except those for the domain example.com
To set up further filters, configure extra search rules that target the same DNS zone. You do not need to create new
DNS zones for each rule unless you want to filter based on the protocol (SIP or H.323) or use different hop counts.
DNS zones for each rule unless you want to filter based on the protocol (SIP or H.323) or use different hop counts.
Note:
you are not recommended to configure search rules with a Mode of Any alias for DNS zones. This will result in
DNS always being queried for all aliases, including those that may be locally registered and those that are not in the
form of URI addresses.
form of URI addresses.
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Cisco Expressway Administrator Guide
Dial Plan and Call Processing