Yes, crossing the border between the two countries is possible since Autumn 2001 but demands a certain amount of preparation and paper chasing on the Sudanese side that should take the better part of two working days. To be honest, it seems as if Sudanese authorities in Kassala are trying to discourage foreigners from attempting this crossing but it is feasible none the less. On the other hand, entry procedures into Eritrea is simplicity itself: show your passport & visa, get your entry stamp and a warm welcome to Eritrea greeting along with it. It should not take more than 5 – 15 minutes, all depending on the length of the queue in front of you.
Make sure that all your Sudanese paperwork is done according to the book and that every single bit of it is perfectly legible (no smudgy stamps or blotches of ink). Everything will be meticulously scrutinized in Kassala and the slightest discrepancy will result in refusal of exit permit. So if you enter the country via Wadi Halfa, *do* endure the hassle and get your registration and travel permit in Wadi Halfa, you will be asked about it. Your travel permit should be renewed in Khartoum so don’t leave town without it and make sure that destination Kassala is included in it.
First thing in the morning, go to the foreigners registration office (maktab al gawasat watasgil al aganeb). Take any minibus running eastwards and ask the driver to be dropped off in front of the building. Get a photocopy of your travel permit(s), of the two first pages of your passport and all pages of your passport that has anything Sudanese in them. Get all necessary forms, fill them out and get the registration stamp in your passport. This operation should take a few hours. Next stage: If you have your own vehicle—> proceed to Customs Office in the eastern outskirts of town and get Customs Clearance. Drive to border early the following day.
If you use public transport, Chicken-buses and boxis go in roto to the border from a place called Khatmiya – Veggie Market (souq al khodar). Vehicles depart when full and do not depart unless they are full. There might be only one vehicle a day, some days none and seldom more than 2 so get there early. The bus/boxy trip is a package deal that includes, apart from the actual journey to the border, also visits to necessary government offices… Take a minibus eastwards from main market and ask to be dropped off at the Khatmiya junction. From there it is a five-ten minutes walk down a gravel road. Once in Khatmiya head straight to an unmarked booth of the Security Police. Give them your passport, assist the bloke in any way you can (they might have problems reading foreign passports) and otherwise treat him with tender loving care. This is where your fate is partially sealed. He will enter the details of your passport in his log book and write down comments about anything that he finds suspicious on a piece of paper that will be handed over to another bloke that joins the journey to the border.
Security Police station in Kassala. Everybody stays in the vehicle while exit permits are processed and Khatmiya comments are reviewed. Next stop: Customs Office. Everybody takes their luggage for inspection, the passengers get a collective customs clearance. The trip to the border can start in earnest. The border caters exclusively for Eritreans and Sudanese, mostly refugees and their families. Experience with foreigners is non-existent so the guy there just obeys orders and checks that all your stamps, etc. are kosher according to some obscure instruction manual. Any missing this or unclear that and you are sent straight back to Kassala (I have actually talked to a German couple that were sent back for such reasons). All fine? Back on the bus and another 30 minutes bus ride. Final stop: Eritrean border post. Welcome to Eritrea. Get your stamp, reserve your seat on the minibus to Tessenei and change your last Sudanese Dinars to Nakfas with the tea-house lady.