LTE modem where I can control the MTU

Saku Ytti saku at
Sat May 2 06:36:35 UTC 2020

On Fri, 1 May 2020 at 19:00, Dovid Bender <dovid at> wrote:

> I currently have an airlink that is connected directly to a raritan console server. The public IP sits on the raritan. The airlink does not seem to have any MTU options. Ideally I would change the MTU on the interface of the LTE modem wich would force the raritan to send all data < 1400 bytes per packet. I never thought about the reverse so we may need something that would tinker with the MSS as well.

Exactly my use-case with ISR4331 + async NIM + 4G NIM (1RU, single
integrated power supply). Call home over 4G with unspecified WAN IP
with IPSEC.

interface Tunnel1
 description OM: OOB IPsec DMVPN - local wire out-of-band
 ip address
 no ip redirects
 no ip proxy-arp
 ip nhrp map x.y.163.1
 ip nhrp map x.y.164.1
 ip nhrp network-id 1
 ip nhrp holdtime 300
 ip nhrp nhs
 ip nhrp nhs
 ip route-cache same-interface
 ip tcp adjust-mss 1350
 load-interval 30
 keepalive 10 3
 tunnel source Cellular0/2/0
 tunnel mode gre multipoint
 tunnel key 1
 tunnel protection ipsec profile OOB
 hold-queue 3584 in
!interface Cellular0/2/0
 description OM: WAN out-of-band - SINGTEL SIM X
 ip address negotiated
 no ip redirects
 no ip proxy-arp
 ip access-group FROM:INTERNET in
 load-interval 30
 dialer in-band
 dialer idle-timeout 0
 dialer watch-group 1
 no ipv6 nd ra suppress
 hold-queue 3584 in
controller Cellular 0/2/0
 lte modem link-recovery rssi onset-threshold -110
 lte modem link-recovery monitor-timer 20
 lte modem link-recovery wait-timer 10
 lte modem link-recovery debounce-count 6


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