The phrase "old router" refers to a device used to connect multiple devices to the internet wirelessly. The term "old" indicates that the router is not new or recent.
That's better than what we could do with older router setups. (nytimes.com)
With EVDO / CDMA networks winding down, Cradlepoint is offering an incentive for users of older routers to upgrade to the latest technology. (evdoinfo.com)
Even if it was fixed (this would be difficult, as this is a problem with the UPnP protocol itself), many older routers still in use would be vulnerable. (howtogeek.com)