WAN Ports: 1 x 10/100Mbps
LAN Ports: 4 x 10/100Mbps
Standard DRAM: 256 MB
Max DRAM: 768 MB
Flash Memory: 256 MB
Protocol: Ethernet - Fast Ethernet
Network Protocols: L2TP, IPSec, FTP, DHCP, DNS, L2TPv3 and DDNS
Routing Protocols: OSPF, RIP-1, RIP-2, BGP, EIGRP, HSRP, VRRP, NHRP, PIM-SM and GRE
Remote Protocols: Telnet, SNMP 3, HTTP, HTTPS and SSH
Encryption: LEAP, DES, Triple DES, SSL, PEAP, TKIP, PKI, 128-bit AES, 192-bit AES and 256-bit AES
This model is EOL and does not have a direct replacement. The closest is the C881-K9 to which you can add licenses (IP services license) to get back to a more direct replacement.
The primary differences between the CISCO881-K9, CISCO881-SEC-K9, CISCO881G-G-K9, CISCO881G-K9, CISCO881GW-GN-A-K9, CISCO881GW-GN-E-K9, CISCO881W-GN-E-K9 are software feature sets. Check with Maximum Midrange if you are unsure what you need or if you are looking for a replacement or addition to your current router.