boot option to set MTU during RHEL install

I am trying to install RHEL-7.9 and it fails to download the installer image LiveOS/squashfs.img and goes into dracut emergency shell. When I tried to pull that image using curl it failed. Looking at the interface, the mtu setting is incorrect (automatically set by dhcp). After changing it to 1500, the download happens.

Now how do I pass this mtu settings in the boot parameter to continue the installation. When I added this boot option ip=::::::dhcp:1500 dracut reports it as unknown value.

The format as per the documents is ip=ip::gateway:netmask:hostname:interface:method:mtu All of these are optional and only required parameters to be specified.

The manual seems to suggest that the syntax you're using is for explicit network configuration:

ip=<client-IP>:[<peer>]:<gateway-IP>:<netmask>:<client_hostname>:<interface>:{none|off|dhcp|on|any|dhcp6|auto6|ibft}[:[<mtu>][:<macaddr>]]
       

where by using ip=::::::dhcp:1500 you're omitting mandatory values; only the values with square brackets [ ] are optional.

I think you need to use an alternative syntax:

 ip=<interface>:{dhcp|on|any|dhcp6|auto6}[:[<mtu>][:<macaddr>]]
       This parameter can be specified multiple times.

       dhcp|on|any|dhcp6
           get ip from dhcp server on a specific interface

       auto6
           do IPv6 autoconfiguration

       <macaddr>
           optionally set <macaddr> on the <interface>. This cannot
           be used in conjunction with the ifname argument for the
           same <interface>.

That requires the interface name (for example eth0) :

 ip=eth0:dhcp:1500