Hi, contents of /etc/nftables.conf (run in dash shell Debian 12.9): ------------------------------- #!/usr/sbin/nft -f flush ruleset table inet filter { chain filter { type filter hook output priority filter; @ih,0,129 == 0 \ accept; } } ------------------------------- Output: nft: evaluate.c:510: expr_evaluate_bits: Assertion `masklen <= NFT_REG_SIZE * BITS_PER_BYTE' failed. It appears this error occurs due to the apparent 16-byte 'NFT_REG_SIZE' limit. contents of /etc/nftables.conf (run in dash shell Debian 12.9): ------------------------------- #!/usr/sbin/nft -f flush ruleset table inet filter { chain filter { type filter hook output priority filter; @ih,0,136 == 0 \ accept; } } ------------------------------- /etc/nftables.conf:16:13-14: Error: Could not process rule: Value too large for defined data type @ih,0,136 == 0 \ ^^ Again, it appears this error should occur due to the 16-byte 'reg-size' limit. The error is printed differently, or is encountered differently because the mask length was divisble by eight. I believe that the error messages should be similar; "Mask Length greater than upper limit of x bits" may be appropriate. What is the best method to view the values of "NFT_REG_SIZE" and "BITS_PER_BYTE" sunny