针对ISR4K，不支持ip accounting命令，该命令在IOS XE的路由器上被去掉了。具体信息可参考如下：
IP accounting is not supported in any IOS-XE router. The 4451 runs IOS-XE so the same rules from the ASR1000 apply here since this was the first platform with IOS-XE. ASR1000 doesn't support IP accounting. There are several bugs that document this:
CSCtx97298
Remove unsupported CLI "show ip accounting"
Externally found moderate (Sev3) bug: R-Resolved
CSCth37116
ASR1000 Disable IP accounting from the CLI
Externally found moderate (Sev3) bug: R-Resolved
There are no specific documents for the 4451 because this device is very new but again, the same thing applies here. This is not supported here as well in the ASR1000s. The replacement for this feature is Flexible Netflow.
NetFlow is a Cisco IOS technology that provides statistics on packets flowing through the router. NetFlow is the standard for acquiring IP operational data from IP networks. NetFlow provides data to enable network and security monitoring, network planning, traffic analysis, and IP accounting.
A comprehensive IP accounting feature that can be used to replace many accounting features, such as IP accounting, Border Gateway Protocol (BGP) Policy Accounting, and persistent caches.
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fnetflow/configuration/xe-3s/fnf-xe-3s-book/fnf-fnetflow.html
https://community.cisco.com/t5/routing/isr-4451-ip-accounting-config/td-p/2541924
https://community.cisco.com/t5/routing/ip-accounting-command-for-isr4321-k9/td-p/2978617
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipapp/configuration/xe-3s/iap-xe-3s-book/iap-ipserv.html
如上所述，该feature可由Flexible Netflow代替。