NFAS with 8 T1s on ISR 4331

[2006nicolas]

Hi Community

I couldn't find an official Cisco document confirming that on the ISRs 43XX or 44XX we can do NFAS with more that 4 T1s.

I am working on a project where we will be installing 1 x 4331 with 2 x NIM-4MFT-T1/E1 cards. Total we will have 8 x T1s configured as PRIs. Our goal is to use 2 "D" channels, one as primary and one sa backup for the whole group.

If anybody can pinpoint a link where Cisco clearly states we can do NFAS with 8 T1s or mentions the limit that would be nice. Theoritcally, an ISR 4331 can support up to 16 T1s if we use the 2 slots and install 2 x NIM-8MFT-T1/E1.

BTW, this is a temporary solution because the final target is to use SIP trunking.

Thx,

Jorge

[Nithin Eluvathingal · Accepted solution]

Only 4 port Configurations guide is available. But have you gone through the below restrictions from the configuration guide.Which says it should be possible to use both slots if it has same DSP type.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/isdn/configuration/15-mt/vi-15-mt-book/vi-nfas-dch-bkup.html

Restrictions for Configuring NFAS with D-Channel Backup

Restrictions are described in "Restrictions for Configuring ISDN Voice Interfaces". In addition, the following apply:

• NFAS is supported with only a channelized T1 controller and, as a result, is ISDN PRI capable.

• NFAS is supported across multiple T1 controllers installed on different slots only if the DSPs of those slots are of the same type. For example, if T1 controllers on slot 1 and slot 2 are combined to form an NFAS group with the T1 in slot 1 being primary, both slots must have the same type of DSP. If these two slots have different DSP types, only those calls using T1 on slot 1 will connect --all calls through T1 on slot 2 will fail with a disconnect cause of "Resource Unavailable/Unspecified (47)."

[2006nicolas]

Nithin

Thanks for pointing to the link below.. It mentions  "Use of a single D channel to control up to 10 PRI interfaces can free one B channel on each interface to carry other traffic. Any hard failure causes a switchover to the backup D channel and currently connected calls remain connected. The backup D channel cannot be used for data transfer."

Here additional information from a 2nd link:
NFAS is supported when the GW is configured as an H.323 GW or SIP (SIP Trunk between CUCM and the ISR)

https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/11_5_1/sysConfig/CUCM_BK_SE5DAF88_00_cucm-system-configuration-guide-1151/CUCM_BK_SE5DAF88_00_cucm-system-configuration-guide-1151_chapter_01001.html?bookSearch=true

Thx, Jorge